Method for producing leather

ABSTRACT

Leather is produced by a process comprising at least two of the following process steps A) to D): A) use of one or more polyelectrolytes in the production of semifinished products or intermediate products, comprising the addition of one or more polyelectrolytes in at least one of the steps (a) to (d) (a) together with from 0 to 1.5% by weight, based on the salted weight, of lime, immediately before or during liming, (b) before or during deliming, (c) before or during bating, (d) together with, altogether, from 0 to 3% by weight, based on the pelt weight, of alkali metal or alkaline earth metal salt, immediately before or during pickling; 
 
B) treatment of the hides during liming in an aqueous liquor with one or more compounds of the formula B.1  
                 
      or the corresponding alkali metal, alkaline earth metal, ammonium or phosphonium salts thereof, R 10  and X 1  to X 4  having the meanings stated in the description, with the proviso that at least two mercapto groups are present in the compound or the compounds B.1; 
 
C) use of degreasing agents of the formula C.1  
                 
    for degreasing pelts, hides or other intermediate stages and semifinished products in leather production, n and R 16  to R 21  having the meanings stated in the description; 
 
D) tanning with the use of a tanning agent which can be prepared by reacting at least one aldehyde of the formula D.1,  
                 
 
 with at least one further identical or different aldehyde of the formula D.1 in the presence of an acidic catalyst and optionally in the presence of at least one further carbonyl compound of the formula D.2  
                 
    Z and R 22  to R 25  having the meanings stated in the description, with the proviso that, when Z corresponds to a single chemical bond or a radical without α-hydrogen atoms, at least one further aldehyde of the formula D.1, in which Z contains α-hydrogen atoms, or at least one further carbonyl compound of the formula D.2 is present.

The present invention relates to a process for the production ofleather, comprising at least two of the following process steps A) toD):

-   A) use of one or more polyelectrolytes for the production of    semifinished products or intermediate products, comprising at least    one of the steps (a) to (d)    -   (a) addition of one or more polyelectrolytes and from 0 to 1.5%        by weight, based on the salted weight, of lime, immediately        before or during liming,    -   (b) addition of one or more polyelectrolytes before or during        deliming,    -   (c) addition of one or more polyelectrolytes before or during        bating,    -   (d) addition of one or more polyelectrolytes and, altogether,        from 0 to 3% by weight, based on the pelt weight, of alkali        metal or alkaline earth metal salt, immediately before or during        pickling;-   B) treatment of the hides during liming in aqueous liquor with one    or more compounds of the formula B.1-    or the corresponding alkali metal, alkaline earth metal, ammonium    or phosphonium salts thereof,-    where:    -   R¹⁰ is hydrogen or C₁-C₁₂-alkyl which is unsubstituted or        substituted by one or more mercapto or hydroxyl groups,    -   X¹ to X⁴, independently of one another, are hydrogen,        C₁-C₄-alkyl, hydroxyl, mercapto or NHR¹¹ and    -   R¹¹ is hydrogen, C₁-C₁₂-alkyl, formyl or C₁-C₄-alkylcarbonyl,    -   with the proviso that at least two mercapto groups are contained        in the compound or the compounds B.1;-   C) use of degreasing agents of the formula C.1-    for degreasing pelts, hides or other intermediate products and    semifinished products in leather production,-    where:    -   R¹⁶ to R¹⁹, independently of one another, are hydrogen or        branched or straight-chain C₁-C₁₀-alkyl,    -   R²⁰ is hydrogen or C₁-C₂₅-alkyl,    -   R²¹ is hydrogen or C₁-C₄-alkyl and    -   n is an integer from 1 to 100,    -   R¹⁶ corresponding to C₁-C₁₀-alkyl when R¹⁸ to R²⁰ are each        hydrogen    -   and at least one of the radicals R¹⁸ to R²⁰ corresponding to        C₁-C₂₅-alkyl when R¹⁶ is hydrogen;-   D) tanning with the use of a tanning agent which can be prepared by    reacting at least one aldehyde of the formula D.1,-    with at least one further identical or different aldehyde of the    formula D.1,-    where:    -   Z is a single chemical bond, unsubstituted or substituted        C₁-C₁₂-alkylene, unsubstituted or substituted        C₅-C₁₂-cycloalkylene or unsubstituted or substituted        C₆-C₁₄-arylene,    -   the reaction being carried out in the presence of an acidic        catalyst and optionally in the presence of at least one further        carbonyl compound of the formula D.2    -   where:    -   R²² to R²⁵, independently of one another, are hydrogen,        unsubstituted or substituted C₁-C₁₂-alkyl, unsubstituted or        substituted C₃-C₁₂-cycloalkyl, unsubstituted or substituted        C₇-C₁₃-aralkyl or unsubstituted or substituted C₆-C₁₄-aryl,    -   with the proviso that at least one further aldehyde of the        formula D.1 in which Z contains α-hydrogen atoms, or at least        one further carbonyl compound of the formula D.2, is present        when Z corresponds to a single chemical bond or to a radical        without α-hydrogen atoms.

The present invention furthermore relates to leather which has beenproduced by the novel process.

In addition to the mechanical operation of fleshing and splitting of therawhides, leather production in the beamhouse substantially comprisesthe physicochemical process steps of soaking, liming and unhairing,deliming, bating, pickling and tanning.

The conventional procedure usually results in large amounts of organicand inorganic wastes and correspondingly highly polluted wastewaters,which lead to increasingly critical problems in the tannery with regardto their disposal.

A critical step in leather production from ecological points of view isunhairing. It is effected, as a rule, more or less completely duringliming, conventionally used and economical unhairing reagents beingsodium sulfide and sodium hydrogen sulfide (often also referred to assodium sulfhydrate). The two salts are usually used in industrialquality and thus in highly contaminated form, industrial sodium sulfidegenerally containing not more than 65% by weight of pure Na₂S andindustrial sodium hydrogen sulfide not more than about 72% by weight ofNaHS.

For safety reasons, both sodium sulfide and sodium hydrogen sulfide canbe used only in a strongly alkaline medium because they release toxicand foul-smelling hydrogen sulfide on acidification. For digesting therawhides and, associated therewith, also for establishing stronglyalkaline conditions, quick lime or milk of lime (slurry of calcium oxideor calcium hydroxide in water) is additionally introduced during liming,which contributes to further inorganic wastewater pollution, inparticular in the subsequent deliming step.

The elimination of the unconsumed sulfides, in particular of thesulfide-containing wastewaters, is also a critical step. If excesssulfide is precipitated, for example with Fe(II) and/or Fe(III) salts,iron sulfide sludges which are complicated to separate off and moreoverfurther salt loads are obtained. On the other hand, corrosion problemsare to be expected on oxidation of the sulfides to give ecologicallyacceptable salts, for example by means of hydrogen peroxide.

In the case of the conventional chrome tanning (production of “wet-blue”leathers), chromium-containing wastewaters are furthermore obtained.Here, the amounts of chromium salts used are typically from 1.5 to 8% byweight or more, based on the pelt weight of the leather. However,considerable portions of the salts are as a rule not bound and arepresent in the wastewater. Although the wastewater can be freed fromconsiderable proportions of chromium, for example by chemical treatmentwith lime and iron salts, this results on the other hand inchromium-containing sludges which have to be disposed of on speciallandfills or worked up by a complicated procedure.

Furthermore, the chromium-containing wastes obtained during splittingand leveling of the hides/leathers—said wastes can account for up to 15%by weight, based on the hide weight—also have to be disposed of by acomplicated procedure.

A comprehensive overview of the (currently) best available technique(BAT) for the tanning of leather is provided in this context by thestudy “Integrated Pollution Prevention and Control (IPPC)—ReferenceDocument on Best Available Techniques for the Tanning of Hides andSkins” published by the European IPPC Office of the European Commissionin May 2001 (available on the Internet under http://eippcb.jrc.es).

It is an object of the present invention to bring about improvements inwaste management in the beamhouse by a procedure adapted with respect tothe disposal requirements in the tanning of leather and hence generallyto provide a process for leather production which protects resources andmoreover gives tanned leathers which meet the high quality requirements.

We have found that this object is achieved by the process defined at theoutset, which, according to the invention, comprises at least two of theprocess steps A) to D) defined in more detail below.

Process step A) comprises adding one or more polyelectrolytes in theproduction of semifinished products and intermediate products in leatherproduction:

-   (a) together with from 0 to 1.5% by weight, based on the salted    weight, of lime, immediately before or during liming,-   (b) before or during deliming,-   (c) before or during bating,-   (d) together with, altogether, from 0 to 3% by weight, based on the    pelt weight, of alkali metal or alkaline earth metal salt,    immediately before or during pickling.

Semifinished products and intermediate products in leather production orin the production of skins are understood as meaning those semifinishedproducts and intermediate products which the hides become after thevarious stages in the production of leather before the actual tanning,known to a person skilled in the art, for example, as pelts and pickledpelts.

Furthermore, the term “lime” mentioned under step (a) of process step A)is used in the context of the terminology customary in leatherproduction and refers to slaked lime, CaO.H₂O (“Ca(OH)₂”).

In process step A), both organic and inorganic polyelectrolytes can beused, where organic polyelectrolytes are also to be understood asmeaning bioorganic polyelectrolytes, e.g. protein hydrolysis products.

Organic polyelectrolytes are generally understood as meaning organicpolymers which have a large number of groups capable of undergoing ionicdissociations and which may be an integral part of the polymer chains ormay be attached to these as side groups. In general, each of the randomrepeat units carries at least one group capable of undergoing ionicdissociation in aqueous solution. In the context of the presentinvention, ionomers are also included among the organicpolyelectrolytes, these being organic polymers in which many repeatingunits carry a group capable of undergoing ionic dissociation, but notevery repeating unit does so. Polymers having only one or two ionizablegroups at the respective chain ends or, in the case of branchedpolymers, having a number of groups capable of undergoing dissociation,corresponding to the number of chain ends, are not included amongpolyelectrolytes in the context of the present invention.

In the novel process, poly bases, poly acids, polyampholytes or the polysalts thereof or mixtures thereof can be used. Poly acids are to beunderstood as meaning those organic polyelectrolytes which dissociate inan aqueous medium with elimination of protons, for example withvinylsulfonic acid, vinylsulfuric acid, vinylphosphonic acid,methacrylic acid or acrylic acid as repeating units. Poly bases are tobe understood as meaning those organic polyelectrolytes which containgroups or radicals which can be protonated by reaction with Brønstedacids, for example polyethylenimines, polyvinylamines orpolyvinylpyridines. Polyampholytes are usually understood as meaningthose polymers which contain both repeating units which dissociate in anaqueous medium with elimination of protons and repeating units which canbe protonated by reaction with Bronsted acids. Poly salts are usuallyunderstood as meaning singly or in particular multiply deprotonated polyacids.

Preferably, synthetic polyelectrolytes are used in process step A) ofthe novel process.

The organic polyelectrolytes used in process step A) of the novelprocess are known as such and preferably contain at least threeidentical or different repeating units of the formulae A.1 to A.4

Polyelectrolytes in the context of the present invention are also to beunderstood as meaning those polymers which have repeating units A.1 toA.4 and are present not in linear form but in branched, crosslinked,hyperbranched or dendrimeric form and in which repeating units A¹, A²and/or A¹* are not exclusively terminal units.

Other organic polyelectrolytes which may be used in the novel processhave at least 3 repeating units of the formulae A.5.a or A.5.b:

it also being possible for disulfonated or polysulfonated repeatingunits to be present as a result of the preparation.

In A.1 to A.5.b, the variables are defined as follows:

-   n is an integer from 3 to 50 000, preferably from 20 to 10 000,    particularly preferably up to 5 000,-   A¹ and A¹* are ionic or ionizable groups of the formulae A.6 to A.13-   in which the variables are defined as follows:-   R¹, in each case independently of one another, are hydrogen, OH, CN,    -   C₁-C₂₀-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl, n-dodecyl, n-hexadecyl or n-eicosyl; preferably        C₁-C₆-alkyl, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl or sec-hexyl, particularly preferably C₁-C₄-alkyl, such        as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,        sec-butyl or tert-butyl;    -   C₂-C₂₀-hydroxyalkyl, for example 2-hydroxy-n-propyl, preferably        ω-C₂-C₂₀-hydroxyalkyl, such as 2-hydroxyethyl,        2-hydroxy-n-propyl, 3-hydroxypropyl, 4-hydroxy-n-butyl,        6-hydroxy-n-hexyl, ω-hydroxydecyl, ω-hydroxy-n-dodecyl,        ω-hydroxy-n-hexadecyl or ω-hydroxyeicosyl;    -   C₆-C₁₄-aryl, for example phenyl, α-naphthyl, β-naphthyl or        9-anthracenyl, in particular phenyl;

C₁-C₆-alkoxy, for example methoxy, ethoxy, n-propoxy, isopropoxy,n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentyloxy, isopentyloxy,n-hexyloxy or isohexyloxy, particularly preferably methoxy, ethoxy,n-propoxy or n-butoxy;

-   -   carboxylic esters, for example COOCH₃, COOC₂H₅, COO-n-C₃H₇,        COO-iso-C₃H₇, COO-n-C₄H₉, COO-iso-C₄H₉, COO-tert-C₄H₉, COO—CH₂CH        (C₂H₅) (C₄H₉), COO—CH₂CH₂OH, COO—CH₂—CH₂—CH₂—OH COO—(CH₂)₄—OH,        COO—(CH₂)₆—OH, COO(CH₂—CH₂—O)_(r)—H or COO(CHCH₃—CH₂—O)_(r)—H,        where r is an integer from 1 to 100, preferably from 2 to 50;    -   carboxamides CO—NR³R⁴, CO—NR³R⁴CH₃ ⁺ or CO—NR³R⁴C₂H₅ ⁺;    -   groups of the formula CO—Y¹—(CH₂)_(m)—NR³R⁴,        CO—Y¹—(CH₂)_(m)—NR³R⁴CH₃ ⁺ or CO—Y¹—(CH₂)_(m)—NR³R⁴C₂H₅ ⁺, where        m is an integer from 0 to 4, preferably 2 or 3, and Y¹ is oxygen        or N—H, and the positive charges occurring in the groups of the        formulae CO—NR³R⁴CH₃ ⁺, CO—NR³R⁴C₂H₅ ⁺, CO—Y¹—(CH₂)_(m)—NR³R⁴CH₃        ⁺ and CO—Y¹—(CH₂)_(m)—NR³R⁴C₂H₅ ⁺ being compensated by opposite        ions, for example Cl⁻ or CH₃SO₄−;

-   R² is hydrogen,    -   C₁-C₂₀-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl, n-dodecyl, n-hexadecyl or n-eicosyl; preferably        C₁-C₆-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl or sec-hexyl, particularly preferably C₁-C₄-alkyl, for        example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,        sec-butyl or tert-butyl;    -   C₃-C₁₂-cycloalkyl, for example cyclopropyl, cyclobutyl,        cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl,        cyclodecyl, cycloundecyl or cyclododecyl; preferably        cyclopentyl, cyclohexyl or cycloheptyl;    -   C₇-C₁₃-aralkyl, preferably C₇- to C₁₂-phenylalkyl, for example        benzyl, 1-phenethyl, 2-phenethyl, 1-phenylpropyl,        2-phenylpropyl, 3-phenylpropyl, neophyl        (1-methyl-1-phenylethyl), 1-phenylbutyl, 2-phenylbutyl,        3-phenylbutyl or 4-phenylbutyl, particularly preferably benzyl;    -   C₆-C₁₄-aryl, for example phenyl, 1-naphthyl, 2-naphthyl,        1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl,        3-phenanthryl, 4-phenanthryl or 9-phenanthryl, preferably        phenyl, 1-naphthyl or 2-naphthyl, particularly preferably        phenyl;    -   C₂-C₂₀-hydroxyalkyl, for example 2-hydroxy-n-propyl, preferably        ω-C₂-C₂₀-hydroxyalkyl, for example 2-hydroxyethyl,        2-hydroxy-n-propyl, 3-hydroxypropyl, 4-hydroxy-n-butyl,        6-hydroxy-n-hexyl, ω-hydroxydecyl, ω-hydroxy-n-dodecyl,        ω-hydroxy-n-hexadecyl or ω-hydroxyeicosyl, very particularly        preferably 2-hydroxyethyl; and

-   R³ and R⁴, independently of one another, are hydrogen or    C₁-C₄-alkyl, for example methyl, ethyl, n-propyl, isopropyl,    n-butyl, isobutyl, sec-butyl or tert-butyl.

-   A² are ionic or ionizable groups, preferably —N(R²)—, —CO—N(R²)—,    —N⁺ (R²)₂— or —CO—N⁺ (R²)₂—, where R² is as above but, in the    special meaning, is defined independently thereof,

-   M is hydrogen, alkali metal ions, for example Li⁺, Na⁺, K⁺, Rb⁺ or    Cs⁺ or a mixture thereof, preferably Na⁺ or K⁺;    -   ammonium ions of the formula N(R⁵)₄ ⁺, where the radicals R⁵,        independently of one another, are:    -   C₁-C₂₀-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl, n-dodecyl, n-hexadecyl or n-eicosyl; preferably        C₁-C₆-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, or sec-hexyl, particularly preferably C₁-C₄-alkyl, for        example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,        sec-butyl or tert-butyl;    -   C₃-C₁₂-cycloalkyl, for example cyclopropyl, cyclobutyl,        cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl,        cyclodecyl, cycloundecyl or cyclododecyl; preferably        cyclopentyl, cyclohexyl or cycloheptyl;    -   C₇-C₁₃-aralkyl, preferably C₇- to C₁₂-phenylalkyl, for example        benzyl, 1-phenethyl, 2-phenethyl, 1-phenylpropyl,        2-phenylpropyl, 3-phenylpropyl, neophyl        (1-methyl-1-phenylethyl), 1-phenylbutyl, 2-phenylbutyl,        3-phenylbutyl or 4-phenylbutyl, particularly preferably benzyl;    -   C₆-C₁₄-aryl, for example phenyl, 1-naphthyl, 2-naphthyl,        1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl,        3-phenanthryl, 4-phenanthryl or 9-phenanthryl, preferably        phenyl, 1-naphthyl or 2-naphthyl, particularly preferably        phenyl;    -   C₂-C₂₀-hydroxyalkyl, for example 2-hydroxy-n-propyl preferably        ω-C₂-C₂₀-hydroxyalkyl, for example 2-hydroxyethyl,        2-hydroxy-n-propyl, 3-hydroxypropyl, 4-hydroxy-n-butyl,        6-hydroxy-n-hexyl, ω-hydroxydecyl, ω-hydroxy-n-dodecyl,        ω-hydroxy-n-hexadecyl or ω-hydroxy-eicosyl, very particularly        preferably 2-hydroxyethyl; and    -   in particular hydrogen.

Mixtures of the abovementioned ions can also be chosen.

Anions, for example halide, preferably chloride or bromide, and sulfate,hydrogen sulfate, phosphate, hydrogen phosphate or dihydrogen phosphate,serve for saturating the positive charges in the polyelectrolytes used.

In on average at least one repeating unit per molecule, R² is nothydrogen, i.e. at least one nitrogen atom is completely alkylated,arylated or aralkylated.

In a preferred embodiment, repeating units A.3 of the polyelectrolytesused according to the invention are such that A¹ is COOH and A¹* isCOO(CH₂—CH₂—O)_(r)—H.

Preferably, at least 15 mol % of the repeating units A¹ in formula A.1or A.3 are selected from COOH or COOM groups, and M is defined as above.

In each case, two of the radicals A¹ and A¹* can be linked to oneanother to form a divalent ring system having 1 to 20 ring members, forexample in the manner of the following formula A.14 (three ringmembers):

In formula A.14, Z¹ is a divalent group, for example CH₂, O or NH,N—C₁-C₂₀-alkyl or N⁻, the negative charge being saturated by one or moreof the abovementioned cations and the alkyl radicals being defined asabove.

The organic polyelectrolytes used in process step A) of the novelprocess preferably contain carboxyl groups, it being possible for thecarboxyl groups to be present as free acids or completely or in acertain percentage as salt, i.e. in neutralized form. It is preferableif a certain percentage of the carboxyl groups have been neutralized.For example, from 20 to 99, particularly preferably from 50 to 95, mol %of neutralized carboxyl groups are suitable.

Very particularly preferably used organic polyelectrolytes are thosehigh molecular weight compounds which are prepared from at least 60 mol% of the monomers acrylic acid, methacrylic acid and maleic acid ormixtures thereof and the relevant salts. These include in particularpolyacrylates or polyacrylic acid/maleic anhydride copolymers having amolar maleic anhydride content of from 1 to 40%, especially from 1 to15%.

In order to obtain the organic polyelectrolytes used in process step A)of the novel process and known per se, polymers or copolymers which arecomposed of one or more known olefinically unsaturated monomers aresynthesized by known processes. Preferred monomers which, in thepolymerization, give the polyelectrolytes used according to theinvention are olefinically unsaturated monobasic or polybasic carboxylicacids. Acrylic acid, methacrylic acid, crotonic acid, fumaric acid andmaleic acid are particularly preferred and acrylic acid, methacrylicacid and maleic acid are very particularly preferred. Acrylic acid,methacrylic acid and maleic acid can also be readily used in the form ofthe anhydride in the polymerization. All monomers can be used in thepolymerization as free acids, as salt in neutralized form correspondingto the above definition and also as a mixture of free acid and salt. Thepolyelectrolytes are synthesized by processes known per se. Thepolymerization is preferably effected by a free radical method, asdescribed, for example, in DE-A 31 38 574.

Comonomers may also be used in the polymerization. Suitable comonomersare, for example,

-   vinyl ethers, such as methyl vinyl ether, ethyl vinyl ether, vinyl    n-propyl ether, vinyl isopropyl ether, n-butyl vinyl ether, vinyl    isobutyl ether or vinyl tert-butyl ether,-   (meth)acrylic acid derivatives, such as methyl acrylate, methyl    methacrylate, ethyl acrylate, ethyl methacrylate, acrylamide,    methacrylamide, tert-butylacrylamide, tert-butyl acrylate,    tert-butyl methacrylate or acrylonitrile,-   olefins, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene,    1-octene, 1-decen, 1,3-butadiene, isobutene, isoprene, vinyl    chloride or vinylidene chloride,-   vinylaromatics, such as styrene or α-methylstyrene,-   maleimide or N-methylmaleimide.-   Mixtures of the abovementioned comonomers are furthermore suitable.

The use of organic polyelectrolytes which contain monomers havinghydrolyzable units, for example of A.5.a or A.5.b, is also considered tobe according to the invention when the hydrolyzable units have beencompletely or partially hydrolyzed.

The organic polyelectrolytes used in process step A) of the novelprocess have a number average molecular weight of from 500 to 150 000 g,preferably from 1 000 to 70 000 g, particularly preferably up to 10 000g. The width of the molecular weight distribution M_(w)/M_(n), is from1.2 to 50, preferably from 1.5 to 15, particularly preferably from 2 to15.

The organic polyelectrolytes used in process step A) of the novelprocess carry on average at least repeating units A.1 to A.4 permolecule, it being possible for these groups or repeating units to beidentical or different. Preferably, the polyelectrolytes used accordingto the invention carry on average at least 4, particularly preferably atleast 5, groups of the formulae A.1 to A.4.

Suitable inorganic polyelectrolytes for the novel process arepolyphosphates, preferably in the form of their alkali metal salts, inparticular the sodium or potassium salts, and soda or potassiumwaterglasses. Furthermore, the inorganic polyelectrolytes to be usedaccording to the invention are also to be understood as meaningaluminosilicates, in particular those of the alkali metals and alkalineearth metals. In particular, members of the group consisting of thephyllosilicates, for example kaolinite, the dioctahedral smectites, inparticular muscovite and montmorillionite (main component of bentonites)and the trioctahedral smectites, in particular hectorite, may bementioned here. In this context, reference may also be made to the priorGerman Patent Application 102 37 259.4.

The polyelectrolytes described can be used at different stages inprocess step A) of the novel process for the production of semifinishedproducts and intermediate products in leather production or in theproduction of skins.

Preferably, the polyelectrolytes described above are used during liming,before or during deliming, before or during bating or before or duringpickling.

A particular aspect of the present invention in process step A) of thenovel process is the use of the polyelectrolytes described above duringliming (step a)) and a further aspect of the present invention is aprocess for treating the hides by using the polyelectrolytes describedabove during liming.

Below, data in % by weight are based on the salted weight, unless statedotherwise.

For the use of the polyelectrolytes described above during liming, it isexpedient substantially to markedly reduce the amount of lime andinstead to add an inorganic basic alkali metal compound, for example ahydroxide or a carbonate of an alkali metal, preferably of sodium orpotassium, very particularly preferably of sodium, and one or more ofthe polyelectrolytes described above. Other suitable inorganic basicalkali metal compounds are alkali metal silicates.

A preferred variant in process step A) of the novel process comprisesreducing the amount of lime used during liming to 0.1 to 1.5,particularly preferably 0.01 to 0.5, % by weight. In anotherparticularly preferred variant, the use of lime is completely dispensedwith.

According to the invention, from 0.001 to 100, preferably from 0.005 to50, particularly preferably from 0.03 to 10, very particularlypreferably from 0.1 to 5, % by weight of one or more polyelectrolytesare added.

The polyelectrolyte or polyelectrolytes can be added individually ortogether with the inorganic basic alkali metal compound or compounds.Furthermore, the addition of one or more polyelectrolytes and of theinorganic basic alkali metal compound or compounds can be effected ineach case in one portion or in a plurality of portions and in each casebefore or during liming.

The addition immediately at the beginning of liming is preferred. Theinvention should also comprise adding, for example, a portion ofpolyelectrolyte immediately before liming or during or at the end ofsoaking and a further portion—together with the inorganic basic alkalimetal compound or compounds—during liming. If it is desired to carry outthe addition of the polyelectrolyte or polyelectrolytes in a pluralityof portions, the ratio of polyelectrolyte in the individual portions isnot critical. It has proven expedient to choose portions of about thesame size. Another conceivable variant is to add from 1.1 to 10 times asmuch polyelectrolyte in the first portion as in the second one; anotherconceivable variant is to add from 1.1 to 10 times as muchpolyelectrolyte in the second portion as in the first one. Analogously,the amount of the inorganic basic alkali metal compound or compounds tobe added can be distributed over a plurality of portions.

In a further variant of process step A) of the novel process, thepolyelectrolytes are modified in situ; for example, polyacrylates orpolymethacrylates can be used as polymeric acids and can be convertedinto the poly-alkali metal salt of the relevant polyelectrolyte by thebasic alkali metal compound used.

According to the invention, the polyelectrolyte or polyelectrolytes canbe added in the absence of a solvent or in solution, preferably inaqueous solution.

In a preferred variant of the novel process, one or more amine compound,in particular one or more hydroxylamine compounds or hydrazine compoundsof the formula A.15.a, A.15.b

where:

-   R⁶ to R⁹, independently of one another, are hydrogen, C₁-C₂₀-alkyl    or C₆-C₁₄-aryl, the alkyl and aryl radicals corresponding to the    meanings mentioned and exemplified under R¹, and-   An⁻ is halide, sulfate, hydrogen sulfate, phosphate, hydrogen    phosphate or dihydrogen phosphate or a mixture of said anions-   are added in addition to the electrolytes described above during    liming (step (a) of process step A)).

In particular, those compounds of the formulae A.15.a and A.15.b inwhich at least one of the radicals R⁶ to R⁹ is hydrogen are used.

Examples of anions An⁻ are halide, preferably chloride or bromide, andfurthermore sulfate, hydrogen sulfate, phosphate, hydrogen phosphateand/or dihydrogen phosphate.

The use of hydroxylamine compounds of the formula A.15.a is preferred.The use of hydroxylamine in the form of the free base is veryparticularly preferred.

If one or more hydroxylamine compounds of the formula A.15.a are used,the amount of basic alkali metal compound can be reduced.

It is particularly advantageous to use one or more hydroxylaminecompounds of the formula A.15.a or A.15.b or one or more hydrazinecompounds of the formula A.16 together with alkali metal hydroxide andalkali metal carbonate in addition to the polyelectrolyte during liming(step (a) of process step A)).

The amount of hydroxylamine compounds of the formula A.15.a or A.15.b orone or more hydrazine compounds of the formula A.16 which is preferablyused during liming is from 0.5 to 10% by weight.

Of course, assistants customary in tanning, for example biocides,enzymes, unhairing agents, surfactants and emulsifiers, may also beadded to the solution of the polyelectrolyte.

A further aspect of the present invention, in process step A) of thenovel process, is the addition of one or more of the polyelectrolytesdescribed above before or during deliming. According to the invention,from 0.001 to 100, preferably from 0.005 to 50, particularly preferablyfrom 0.03 to 10, very particularly preferably from 0.1 to 5, % by weightof one or more polyelectrolytes are added.

A further aspect of the present invention, in process step A) of thenovel process, is the addition of one or more of the polyelectrolytesdescribed above before or during bating. According to the invention,from 0.001 to 100, preferably from 0.005 to 50, particularly preferablyfrom 0.03 to 10, very particularly preferably from 0.1 to 5, % by weightof one or more polyelectrolytes are added.

A further particular aspect of the present invention, in process step A)of the novel process, is the use of the polyelectrolytes described abovebefore or during pickling, preferably immediately before pickling, and afurther aspect of the present invention is a process for treating hidesby using the polyelectrolytes described above before or during pickling.

For the use of the polyelectrolytes described above before or duringpickling in process step A) of the novel process, the amount (usuallyfrom 5 to 10% by weight) of alkali metal halide used, usually sodiumchloride, may expediently be reduced and instead a novel amount of oneor more polyelectrolytes may be used.

According to the invention, from 0.001 to 100, preferably from 0.005 to50, particularly preferably from 0.03 to 10, very particularlypreferably from 0.1 to 5, % by weight of one or more polyelectrolytesare used.

According to the invention, furthermore from 0 to 3, preferably from 0to 1, particularly preferably from 0 to 0.5, % by weight of one or moreinorganic alkali metal or alkaline earth metal salts, for example alkalimetal halides, such as sodium fluoride, sodium chloride, sodium bromide,potassium chloride or potassium bromide or mixtures thereof, are usedbefore or during pickling, preferably immediately before pickling inprocess step A) of the novel process. It is also possible to add otherinorganic alkali metal salts, for example Glauber's salt (sodiumsulfate), or inorganic alkaline earth metal salts, such as magnesiumchloride or magnesium sulfate. In a very particularly preferred variant,at least 0.01 to 0.2% by weight of inorganic alkali metal or alkalineearth metal salts, in particular sodium chloride, is used; in anothervery particularly preferred variant, the use of alkali metal or alkalineearth metal salts is completely dispensed with. Very particularlypreferably, not more than 0.05% by weight of alkali metal halide, inparticular sodium chloride, is used.

The addition of one or more polyelectrolytes and alkali metal oralkaline earth metal salts in process step A) of the novel process, ifan addition of alkali metal or alkaline earth metal salts is desired,can be effected separately or together and in each case immediatelybefore or during pickling. Furthermore, the addition of one or morepolyelectrolytes and—if desired—alkali metal or alkaline earth metalsalts can be effected in each case in one portion of in a plurality ofportions and in each case before or during pickling. It is alsoaccording to the invention, for example, to add a portion ofpolyelectrolyte immediately before pickling and a furtherportion—together with alkali metal or alkaline earth metal salt—duringpickling. If it is desired to carry out the addition of thepolyelectrolyte or polyelectrolytes in a plurality of portions, theratio of polyelectrolyte in the individual portions is not critical. Ithas proven expedient to choose portions of about the same size. Anotherconceivable variant comprises adding from 1.1 to 10 times as muchpolyelectrolyte in the first portion as in the second one; anotherconceivable variant comprises adding from 1.1 to 10 times as muchpolyelectrolyte in the second portion as in the first one. Analogously,the amount of the alkali metal or alkaline earth metal salts to be addedcan be distributed over a plurality of portions.

The polyelectrolyte or polyelectrolytes can be added in process step A)of the novel process in the absence of a solvent or in solution,preferably in aqueous solution, it being possible also to add assistantscustomary in tanning, for example biocides, acids, such as sulfuricacid, formic acid, hydrochloric acid, oxalic acid or acetic acid, acidicsalts, buffers, fatliquoring agents, resin tanning agents, vegetabletanning agents and fillers, for example kaolin or ligninsulfonate, tothe solution.

The residence time of the unsplit hides in the pickle in process step A)of the novel process is usually from 10 minutes to 24 hours, preferablyfrom 15 minutes to 2 hours, particularly preferably from 15 to 45minutes. With the use of split hides, shorter residence times arepossible, as is known to a person skilled in the art.

The pickling takes place under conditions otherwise customary intanning, the temperature is from 10 to 35° C. and the pressure is from 1to 10 bar, atmospheric pressure being particularly expedient.

If, according to the invention, one or more polyelectrolytes are addedin process step A) of the novel process before or during liming, theamount of added polyelectrolyte in the pickle can be reduced. In anextreme case, the addition of further polyelectrolyte during orimmediately before pickling can be completely dispensed with.

In a particular variant, in process step A) of the novel process, from0.1 to 10, preferably from 0.5 to 10, % by weight of one or morepolyelectrolytes are added during liming, and the addition of furtherpolyelectrolyte can be dispensed with in the further steps, deliming,bating and pickling, because the concentration of polyelectrolyte issufficiently high. In a preferred variant of the novel process, in whichthe addition of lime is completely dispensed with, it is possible todispense with a separate deliming step; particularly in this variant, afurther addition of polyelectrolyte can be dispensed with.

Process step B) of the present invention comprises the unhairing of thehides with one or more compounds of the formula B.1

or the corresponding alkali metal, alkaline earth metal, ammonium orphosphonium salts thereof,

-   with the proviso that at least two mercapto groups are contained in    the compound or compounds B.1,-   where:-   R¹⁰ is hydrogen or C₁-C₁₂-alkyl which is unsubstituted or    substituted by one or more mercapto or hydroxyl groups, for example    -   methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,        sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,        neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl,        sec-hexyl or n-decyl, particularly preferably C₁-C₄-alkyl, such        as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,        sec-butyl and tert-butyl;    -   hydroxymethyl, 2-hydroxyethyl, 1,2-dihydroxyethyl,        3-hydroxy-n-propyl, 2-hydroxyisopropyl, ω-hydroxy-n-butyl,        ω-hydroxy-n-decyl, HS—CH₂—, HS—(CH₂)₂— or HS—(CH₂)₃—;    -   in particular hydrogen;-   X¹ to X⁴, independently of one another, are hydrogen;    -   C₁-C₄-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl or tert-butyl;    -   hydroxyl, mercapto or NHR¹¹, in particular hydroxyl or mercapto;        and-   R¹¹ is hydrogen, formyl,    -   C₁-C₁₂-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl or n-decyl, particularly preferably        C₁-C₄-alkyl, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl or tert-butyl; or    -   C₁-C₄-alkylcarbonyl, for example acetyl, C₂H₅—C═O, n-C₃H₇—C═O,        iso-C₃H₇—C═O, n-C₄H₉—C═O, iso-C₄H₉—C═O, sec-C₄H₉—C═O or        tert-C₄H₉—C═O.

Preferably at least one group X¹ to X⁴ is a hydroxyl group, particularlypreferably at least two groups X¹ to X⁴ are hydroxyl groups.

Examples of the corresponding alkali metal and alkaline earth metalsalts are in particular the mono- and disodium salts, mono- anddipotassium salts and potassium sodium salts of the compounds of theformula B.1, and furthermore the corresponding calcium and magnesiumsalts. Further examples are the ammonium salts and primary, secondary,tertiary and in particular quaternary mono- and diammonium salts andphosphonium salts. Of course, mixtures of compounds of the formula B.1and the corresponding alkali metal or alkaline earth metal salts orammonium or phosphonium salts thereof may also be used. The alkali metalsalts are preferably used.

Preferred mono- and diammonium salts have, as cations, those of theformula N(R¹²) (R¹³) (R¹⁴) (R¹⁵)⁺, where R¹² to R¹⁵, in each caseindependently of one another, are hydrogen, C¹-C₁₂-alkyl, phenyl orCH₂—CH₂—OH. Examples are tetramethylammonium, tetraethylammonium,methyldiethanolammonium and n-butyldiethanolammonium. Preferred mono-and diphosphonium salts have, as cations, those of the formula P(R¹²)(R¹³) (R¹⁴) (R¹⁵)⁺, where R¹² to R¹⁵ are defined as above.

Very particularly preferably, one or more 1,4-dimercaptobutanediols ofthe formulae B.1.a, B.1.a′ and B.1.b

or the corresponding alkali metal or alkaline earth metal salts thereofare used in process step B) of the novel process. B.1.a and B.1.a′ arealso referred to as dithiothreitol, and B.1.b also as dithioerythrol.The use of racemic dithiothreitol is very particularly preferred. B.1.a,B.1.a′ and B.1.b are virtually odorless, readily meterable and readilywater-soluble compounds.

The compounds B.1.a or B.1.a′ and B.1.b are known and are commerciallyavailable, for example, from Aldrich or AGROS Chemicals. Further memberscan be synthesized as described in U.S. Pat. No. 4,472,569 or in J.Chem. Soc. 1949, 248 or by analogous reactions.

In general, an amount of from 0.1 to 5, preferably from 0.5 to 2.5,particularly preferably from 0.75 to 1.5, % by weight, based on the hideweight or salt weight of the hides, furs or skins, of compound B.1 aresufficient in process step B) of the novel process.

In process step B) of the novel process, the hides, furs or skins arepreferably treated with one or more compounds of the formula B.1 duringliming or during sulfiding, in particular under either hair-destroyingor hair-preserving conditions. This makes it possible to manage with aconcentration of less than 1% by weight of Na₂S or NaHS with an equallylarge effect with regard to the removal of horny substances duringliming or sulfiding, instead of the usual concentration of about 4% byweight of Na₂S or NaHS or even slightly more.

In one variant of process step B) of the novel process, one or morecompounds of the formula B.1 can be used together with thiols known fromtanning, for example mercaptoethanol or thioglycolic acid, duringliming. Preferably, less than 0.5% by weight of mercaptoethanol orthioglycolic acid is used here.

However, the use of Na₂S or NaHS or other foul-smellingsulfur-containing reagents is preferably dispensed with in process stepB) of the novel process.

The hides are treated in process step B) of the novel process in anaqueous liquor. The liquor ratio is from 1:10 to 10:1, preferably from1:2 to 4:1, particularly preferably up to 3:1, based on the hide weightor salt weight of the hides.

Process step B) of the novel process is carried out at a pH of from 7 to14, preferably from 8 to 13, particularly preferably from 9 to 12.5.

The pH can be established by adding up to 3% by weight, based on theliquor, of lime. However, the amount of lime can also be substantiallyreduced. In a preferred variant of the novel process, the use of lime isdispensed with. In the preferred embodiment, one or more inorganic basicalkali metal compounds, for example one or more hydroxides or carbonatesof alkali metals, preferably of sodium or potassium, very particularlypreferably of sodium, are added. Other suitable inorganic basic alkalimetal compounds are alkali metal silicates. Basic amines, for exampleammonia, methylamine, dimethylamine, ethylamine or triethylamine, orcombinations of alkali metal compound and one or more basic amines, mayalso be added.

In addition to water, further organic solvents may be present in theliquor, for example up to 20% by volume of ethanol or isopropanol.

Process step B) of the novel process can be carried out in the vesselswhich are customary in tanning and in which liming is usually effected.The novel process is preferably carried out in rotatable drums withinternal fittings. The speed is usually from 0.5 to 100/min, preferablyfrom 1.5 to 10/min, particularly preferably from 2 to 6/min.

The pressure and temperature conditions for carrying out process step B)of the novel process are generally not critical. The procedure atatmospheric pressure has proven suitable; a pressure increased to 10 baris also conceivable. Suitable temperatures are from 10 to 45° C.,preferably from 15 to 35° C., particularly preferably from 20 to 30° C.

The compound or compounds of the formula B.1 can be metered at thebeginning of the liming process, but it is also possible for the hidesfirst to be softened under basic conditions and one or more compounds ofthe formula B.1 to be metered only after some time. The metering can beeffected in one step, i.e. the total amount of the compound or compoundsB.1 used is metered in one step; however, B.1 can also be metered inportions or continuously.

Process step B) of the novel process can be carried out in a period offrom 10 minutes to 48 hours, preferably from 1 to 36 hours, particularlypreferably from 3 to 15 hours.

Of course, assistants customary in tanning, for example phosphines, suchas triphenylphosphine or tris(2-carboxyethyl)phosphine hydrochloride,and furthermore hydroxylamine, urea, guanidine or guanidinehydrochloride, hydrazine, biocides, enzymes, surfactants andemulsifiers, can be added for carrying out process step B) of the novelprocess.

Pelts unhaired in an excellent manner can be produced by process step B)of the novel process. Surprisingly, it is also found that the epidermisis completely or at least substantially detached after only a shorttreatment time.

According to the invention, degreasing agents of the formula C.1

are used in process step C) for degreasing pelts, hides or furtherintermediate products and semifinished products in leather production.In formula C.1, the variables are defined as follows:

-   R¹⁶ to R¹⁹, independently of one another, are hydrogen or    -   C₁-C₁₀-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl or        n-decyl; preferably C₁-C₆-alkyl, for example methyl, ethyl,        n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,        n-pentyl, isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl,        isoamyl, n-hexyl, isohexyl or sec-hexyl, particularly preferably        C₁-C₄-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl or tert-butyl;-   R²⁰ is hydrogen or    -   C₁-C₂₅-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl, n-dodecyl, n-hexadecyl or n-eicosyl; preferably        C₁-C₆-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl or sec-hexyl, particularly preferably C₁-C₄-alkyl, for        example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,        sec-butyl or tert-butyl;-   R²¹ is hydrogen or    -   C₁-C₄-alkyl, for example methyl, ethyl, n-propyl, isopropyl,        n-butyl, sec-butyl, isobutyl or tert-butyl;    -   R¹⁶ being selected from C₁-C₁₀-alkyl when R¹⁸ to R²⁰ are each        hydrogen    -   and at least one radical from among R¹⁸ to R²⁰ being selected        from C₁-C₂₅-alkyl when R¹⁶ is hydrogen,-   n is an integer from 1 to 100, preferably from 1 to 25, particularly    preferably from 3 to 15.

The degreasing agent used in process step C) of the novel process hasvery good efficiency in the emulsifier degreasing. Particularly in anaqueous medium, it has a good emulsifying effect on natural fats andoils and emulsifies them in such a way that the fat and oil componentscan be readily washed out of the animal hide with water.

The degreasing agent used in process step C) of the novel processpreferably contains a mixture of alcohol alkoxylates, based on from 1 to3 different alcohols C.2

particularly preferably on a single alcohol C.2 or two differentalcohols C.2. If mixtures of degreasing agents based on differentalcohols C.2 are employed, the number of carbon atoms of the alcoholradical and/or the type of branching may differ.

The main chain of the alcohols C.2 preferably has from one to 4,particularly preferably from 1 to 3, branches, provided that the chainlength permits more than one branch in the middle of the chain. Thesebranches, independently of one another, generally have 1 to 10,preferably 1 to 6, particularly preferably 2 to 4, very particularlypreferably 2 or 3, carbon atoms. Particularly preferred branches areaccordingly ethyl, n-propyl or isopropyl groups.

The radical of the alcohol C.2 has 5 to 30 carbon atoms. Since C.2 hasat least one branch with at least one carbon atom, the main chaincomprises 4 to 29 carbon atoms. Preferably, C.2 has up to 25 carbonatoms, particularly preferably 10 to 20, carbon atoms. This means thatthe main chain has preferably 5 to 24, particularly preferably 9 to 19,carbon atoms. Very particularly preferably, the main chain has 9 to 15carbon atoms and the other carbon atoms of C.2 are distributed over oneor more branches.

The preparation of the branched alcohols C.2 which are required for thepreparation of the alcohol alkoxylates used in process step C) of thenovel process is effected by methods known to a person skilled in theart. A general synthesis route for the preparation of branched alcoholsis, for example, the reaction of aldehydes or ketones by the Guerbetreaction or using Grignard reagents. Instead of the Grignard reagents,aryl- or alkyllithium compounds, which have higher reactivity, may alsobe used.

The alcohol alkoxylates used, which are contained in the degreasingagents used in process step C) of the novel process, are based on thereaction products of branched alcohols C.2 with alkylene oxide which ispreferably selected from the group consisting of ethylene oxide,propylene oxide and butylene oxide. It is possible to react a singlealcohol C.2 with different alkylene oxides from among the statedalkylene oxides, e.g. ethylene oxide and propylene oxide, it beingpossible to obtain alcohol alkoxylates which in each case have blocks ofa plurality of units of an alkylene oxide, e.g. ethylene oxide, inaddition to blocks of a plurality of units of a further alkylene oxide,e.g. propylene oxide.

The amounts of alkylene oxide used are from 1 to 100, preferably from 1to 25, particularly preferably from 3 to 15, very particularlypreferably from 5 to 12, mol of alkylene oxide per mole of alcohol. Inthe alcohol alkoxylates used according to the invention, the degree ofalkoxylation achieved has a broad distribution and, depending on theamount of alkylene oxide used, may be from 0 to 100 mol of alkyleneoxide per mole of alcohol. It has been found that the molecular weightdistribution which is achieved by reacting the alcohols C.2 used withalkylene oxides and which is based on the degree of alkoxylation of thealcohols does not correspond to a Gaussian distribution. Such a Gaussiandistribution is obtained in the case of alkoxylation of oxo alcohols(industrial alcohols which contain about 60% by weight of linearalcohols and about 40% by weight of alcohols branched with methylgroups) to give alcohol alkoxylates as used in the prior art in leatherdegreasing agents, and in the case of alkoxylation of alkylphenols, thealkoxylation products of which have been the most successful to date inthe degreasing of leather. The degree of alkoxylation and hence themolecular weight distribution is substantially broader in the case ofalkoxylation of the alcohols C.2 used in process step C) of the novelprocess.

If the degreasing agent used in process step C) of the novel processcontains a mixture of alcohol alkoxylates which are based on differentalcohols and/or have been reacted with a different amount or differentalkylene oxides, these may be present in any desired ratios. If thedegreasing agent contains, for example, two different alcoholalkoxylates, they may be present in ratios of from 20:1 to 1:1,preferably from 9:1 to 1:1. In the case of three different alcoholalkoxylates, it is also possible for one of the components to be presentin excess relative to the other two components. It is also possible for2 components to form the main part of the alcohol alkoxylates and foronly small amounts of the third component to be present. Furthermore, itis possible for all three components to be contained in the degreasingagent in about the same amounts.

The HLB values of the alcohol alkoxylates used as degreasing agents inprocess step C) of the novel process are in general from 8 to 16,preferably from 9 to 14.

The alcohol alkoxylates are prepared from the branched alcohols C.2 byreaction with alkylene oxides. The reaction conditions are known to aperson skilled in the art. In general, the reaction is carried out overan alkali metal catalyst. Usually, NaOH or KOH is used. It is alsopossible to use Ca(OH)₂, Ba(OH)₂, Sr(OH)₂ or hydrotalcite as catalysts.Furthermore, complex metal cyanides, e.g. Zn₃[Co(CN)₆]₂ can also be usedas catalysts. The latter catalysts lead as a rule to narrower molecularweight distributions. The reaction is preferably effected in the absenceof water. The reaction temperature is in general from 70 to 180° C.

The novel degreasing agents can be used in different process stages inwhich the use of a degreasing agent is expedient or necessary, inleather or fur production. Thus, it can be used, for example, insoaking, liming, deliming, bating, pickling and/or tanning and afterdepickling, in the processing of wet blue or wet white, in the wetfinishing process and in the working-up of crust leathers. Theseindividual process stages are known to a person skilled in the art.

Depending on the process stage in which the novel degreasing agents areemployed, the degreasing agents can be used in combination with furthercomponents. Such components are known to a person skilled in the art.Suitable components are, for example, further formulation agents, suchas wetting agents, raw components having a surfactant effect, e.g. ethersulfates or dispersants; antifoams, such as paraffins and siloxanes;carrier oils, such as higher alkanes, aromatics-rich vegetable orsynthetic oils, white oil or mineral oil; other nonionic, anionic,cationic and/or amphoteric surfactants.

Process step C) of the novel process can be carried out in the liquor orwithout a liquor. If the process is carried out without a liquor, thenovel degreasing agent is added to the hides, skins, pelts or furtherintermediate products to be degreased, and this is followed by milling.

The exact process conditions are dependent on the process stage in whichthe degreasing agent used in process step C) of the novel process isused. The following data are therefore general process conditions,without any detailed discussion of the specific special features, whichare to be taken into account in the individual process stages. These areknown to a person skilled in the art.

The alcohol alkoxylates contained in the degreasing agent used inprocess step C) of the novel process are used in general in an amount offrom 0.5 to 5, preferably from 1 to 3, % by weight, based on the weightof the hides, skins, pelts or other intermediate products, in leatherand fur production. These data relate to the total content of thealcohol alkoxylates contained in the degreasing agent used in processstep C) of the novel process. With the use of a plurality of alcoholalkoxylates, the proportion of the individual alcohol alkoxylates isobtained from the abovementioned ratios. The degree of degreasinggenerally increases with the amount used, up to the stated upper limit,the degree of degreasing depending, inter alia, on the natural fatcontent of the animal hides. An addition of larger amounts of alcoholalkoxylates is not expedient since no further improvement in the degreeof degreasing is achieved or the quality may be impaired. Furthermore,it should be ensured that the saturation concentration of the alcoholalkoxylate used is not exceeded.

The novel process is carried out in general at a pH of from 2 to 10. ThepH varies from acidic to basic depending on the process stage. Theeffect of the pH on the degree of degreasing is generally small in thecase of the nonionic surfactants used according to the invention.

The salt contents present during the degreasing process correspond tothe salt contents usually used in the various process stages. The saltcontent of the liquor may be in general from 0 to 100, preferably from 0to 3, g of NaCl/l.

The temperature when carrying out the novel process is in general from15 to 65° C., preferably from 20 to 55° C., in particular from 28 to 40°C.; it must however be at least 5° C. below the melting point ofcollagen. The temperature may also differ in the different processstages. Thus, higher temperatures can be used after the tanning of theleather than in the preceding steps since temperatures which are toohigh prior to tanning can adversely affect the quality of the leathersor skins to be produced. An increase in the temperature generally leadsto an increase in the degree of degreasing.

The duration of the process in turn depends on the process stage inwhich the novel degreasing agent is used. In general, the duration ofthe degreasing is from 0.5 to 10, preferably from 0.5 to 5, particularlypreferably from 0.5 to 3, hours. The degree of degreasing generallyincreases with increasing duration, until a maximum is reached.

The liquor length should be chosen at least sufficiently long formicelle formation to be present, so that the degreasing agent candisplay its effect. For good efficiencies, a plurality of liquors whichare as short as possible, with changing baths, are preferably used.

With the degreasing agents used in process step C) of the novel process,efficiencies of from at least 50 to 55% can be achieved in leatherdegreasing. The efficiency in % is defined as the dissolved amount offat, i.e. the difference in the fat content before the degreasing (x₀)and after the degreasing (x₁), as a ratio of the fat content before thedegreasing (x₀), i.e. as (x₀−x₁)·100/x₀.

After the degreasing, the degreased material is generally washed withwater. In the preferred emulsifier degreasing, the wastewater pollutionis reduced to the substances natural fat and surfactant. If desired,these substances can be separated from the aqueous phase by heating theaqueous mixture. At elevated temperatures, the nonionic surfactants usedaccording to the invention have poorer solubility. As a result of theconsequent loss of emulsifier activity, separation of the emulsionoccurs. Methods for separating the water from the natural fat and thesurfactant are known to a person skilled in the art.

Process step D) of the novel process comprises pretanning, tanning orretanning of pretreated pelts with tanning agents obtainable by reactingaldehydes of the formula D.1

in the presence of an acidic catalyst and optionally in the presence ofat least one further carbonyl compound of the formula D.2

with the proviso that, if Z is a single chemical bond or a radicalwithout α-hydrogen atoms, at least one further aldehyde of the formulaD.1 in which Z contains α-hydrogen atoms or at least one furthercarbonyl compound of the formula D.2 is present.

In formula D.1, the variables are defined as follows:

-   Z is a single chemical bond,

C₁-C₁₂-alkylene, for example —CH₂—, —CH₂—CH₂—, —(CH₂)₃—, —(CH₂)₄—,—(CH₂)₅—, —(CH₂)₆—, —(CH₂)₇—, —(CH₂)₈—, —(CH₂)₉—, —(CH₂)₁₀—, —(CH₂)₁₁—,—(CH₂)₁₂—, cis- or trans-CH═CH—, Z- or E-CH₂—CH═CH—; preferably —CH₂—,—CH₂—CH₂—, —(CH₂)₃—, —(CH₂)₄—;

-   -   substituted C₁-C₁₂-alkylene, for example —CH(CH₃)—, —CH(C₆H₅)—,        —CH(CH₃)—CH₂—, syn-CH(CH₃)—CH(CH₃)—, anti-CH(CH₃)—CH(CH₃)—,        syn-CH(CH₃)—CH(C₆H₅)—, anti-CH(CH₃)—CH(C₆H₆)—, —(CH(CH₃))_(3—;)    -   unsubstituted or substituted C₅-C₁₂-cycloalkylene, for example        trans- or cis-1,2-cyclopentylene, trans- or        cis-1,3-cyclopentanylene, trans- or cis-1,3-cyclopent-4-enylene,        trans- or cis-1,4-cyclohexanylene, trans- or        cis-1,4-cyclohex-2-enylene, trans- or cis-1,3-cyclohexylene,        trans- or cis-1,2-cyclohexylene, suitable substituents in each        case being one or more C₁-C₄-alkyl groups, such as methyl,        ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or        tert-butyl, or one or more halogen atoms, such as fluorine,        chlorine, bromine or iodine; or    -   unsubstituted or substituted C₆-C₁₄-arylene, for example        para-phenylene, meta-phenylene, ortho-phenylene,        1,2-naphthylene, 1,3-naphthylene, 1,4-naphthylene,        1,5-naphthylene, 1,6-naphthylene, 1,7-naphthylene,        1,8-naphthylene, 2,3-naphthylene, 2,7-naphthylene,        2,6-naphthylene, 1,4-anthrylene, 9,10-anthrylene or        p,p′-biphenylene, suitable substituents in each case being one        or more C₁-C₄-alkyl groups, such as methyl, ethyl, n-propyl,        isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl, or one or        more halogen atoms, such as fluorine, chlorine, bromine or        iodine.

In formula D.2, the variables are defined as follows:

-   R²² to R²⁵, independently of one another, are hydrogen,    -   C₁-C₁₂-alkyl, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl or n-dodecyl; preferably C₁-C₆-alkyl, such as methyl,        ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,        tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,        1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl or sec-hexyl,        particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,        n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl,        very particularly preferably methyl;    -   unsubstituted or substituted C₃-C₁₂-cycloalkyl, such as        cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,        cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl or        cyclododecyl; preferably cyclopentyl, cyclohexyl, cycloheptyl,        2-methylcyclopentyl, 3-methylcyclopentyl,        cis-2,4-dimethylcyclopentyl, trans-2,4-dimethylcyclopentyl        2,2,4,4-tetramethylcyclopentyl, 2-methylcyclohexyl,        3-methylcyclohexyl, 4-methylcyclohexyl,        cis-2,5-dimethylcyclohexyl, trans-2,5-dimethylcyclohexyl,        2,2,5,5-tetramethylcyclohexyl, 2-methoxycyclopentyl,        2-methoxycyclohexyl, 3-nethoxycyclopentyl, 3-methoxycyclohexyl,        2-chlorocyclopentyl, 3-chlorocyclopentyl,        2,4-dichlorocyclopentyl, 2,2,4,4-tetrachlorocyclopentyl,        2-chlorocyclohexyl, 3-chlorocyclohexyl, 4-chlorocyclohexyl,        2,5-dichlorocyclohexyl, 2,2,5,5-tetrachlorocyclohexyl,        2-thiomethylcyclopentyl, 2-thiomethylcyclohexyl,        3-thiomethylcyclopentyl or 3-thiomethylcyclohexyl;    -   C₇-C₁₃-aralkyl, preferably C₇- to C₁₂-phenylalkyl, such as        benzyl, 1-phenethyl, 2-phenethyl, 1-phenylpropyl,        2-phenylpropyl, 3-phenylpropyl, neophyl(l-methyl-l-phenylethyl),        1-phenylbutyl, 2-phenylbutyl, 3-phenylbutyl or 4-phenylbutyl,        particularly preferably benzyl;    -   C₆-C₁₄-aryl, such as phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl,        2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl,        3-phenanthryl, 4-phenanthryl or 9-phenanthryl, preferably        phenyl, 1-naphthyl or 2-naphthyl, particularly preferably        phenyl, unsubstituted or substituted by one or more        -   C₁-C₁₂-alkyl groups, such as methyl, ethyl, n-propyl,            isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,            n-pentyl, isopentyl, sec-pentyl, neopentyl,            1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,            n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl or n-dodecyl;            preferably C₁-C₆-alkyl, such as methyl, ethyl, n-propyl,            isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,            n-pentyl, isopentyl, sec-pentyl, neopentyl,            1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,            particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,            n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or            tert-butyl;        -   halogens, such as fluorine, chlorine, bromine or iodine,            chlorine and bromine being preferred;        -   C₁-C₁₂-alkoxy groups, preferably C₁-C₆-alkoxy groups, such            as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy,            isobutoxy, sec-butoxy, tert-butoxy, n-pentyloxy,            isopentyloxy, n-hexyloxy or isohexyloxy, particularly            preferably methoxy, ethoxy, n-propoxy or n-butoxy.

In a preferred embodiment, R²² and R²³ or R²² and R²⁴ are covalentlybonded to one another with formation of a 4- to 13-membered ring. Forexample, R²² and R²³ together may be: —(CH₂)₄—, —(CH₂)₅—, —(CH₂)₆,—(CH₂)₇—, —CH(CH₃)—CH₂—CH₂—CH(CH₃)— or —CH(CH₃)—CH₂—CH₂—CH₂—CH(CH₃)—.

-   R²² and R²³ are preferably each hydrogen.-   Z is very particularly preferably —(CH₂)₃—.

The reaction for the preparation of the tanning agents used in processstep D) of the novel process is preferably effected by heating D.1 to atemperature of from 30 to 130° C., in particular from 20 to 100° C.,very particularly preferably from 50 to 80° C. The reaction can becarried out at any desired pressures from 0.1 to 100 bar, atmosphericpressure being preferred. The reaction can be effected in the presenceof a solvent, for example in the presence of hydrocarbons, preferablytoluene, petroleum ether or n-heptane. Halogenated hydrocarbons, forexample chloroform, are in principle also suitable. The reaction inaqueous solution or aqueous dispersion is preferred.

Dehydrating agents may be added for accelerating the reaction, but theaddition of dehydrating agents is not necessary. If the reaction iscarried out in water as a solvent, the addition of dehydrating agents isof course not reasonable.

Catalysts used are acidic catalysts, for example phosphoric acid, formicacid, acetic acid, acidic silica gels or dilute or concentrated sulfuricacids. If nonaqueous solvents are employed, the use of P₂O₅ or amolecular sieve is also conceivable. Usually, from 0.1 to 20, preferablyfrom 1 to 10, mol %, based on the amount of compound(s) D.1, of catalystare used.

A reasonable reaction time for the reaction is from 10 minutes to 24hours, preferably from one to three hours.

After the heating, working-up is usually effected by first neutralizingthe acid, for example with aqueous alkali metal hydroxide solution orwith aqueous alkali metal carbonate solution or with solid basic alkalimetal compounds, for example alkali metal hydroxide, alkali metalcarbonate or alkali metal bicarbonate. The volatile components of thereaction mixture can then be distilled off. As a rule, heating to 40 to80° C. under reduced pressure, for example from 10 to 100 mbar, isexpedient for this purpose.

In a preferred embodiment, aldehydes of the formula D.1 are reacted withfrom 1 to 1 000, preferably from 10 to 500, particularly preferably from20 to 200, mol % of at least one further carbonyl compound, wherecarbonyl compounds are to be understood as meaning aldehydes andketones.

The aldehydes and ketones used as further reactants preferably carry α-Hatoms. Particularly preferred aldehydes and ketones are those of theformula D.2′

where R²⁶ to R²⁸, independently of one another, are hydrogen,

-   C₁-C₁₂-alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl,    isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl,    neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl,    sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl, n-decyl or    n-dodecyl; preferably C₁-C₆-alkyl, such as methyl, ethyl, n-propyl,    isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl,    isopentyl, sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl,    n-hexyl, isohexyl, sec-hexyl, particularly preferably C₁-C₄-alkyl,    such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl,    sec-butyl or tert-butyl, very particularly preferably methyl;-   unsubstituted or substituted C₃-C₁₂-cycloalkyl, such as cyclopropyl,    cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl,    cyclononyl, cyclodecyl, cycloundecyl or cyclododecyl; preferably    cyclopentyl, cyclohexyl, cycloheptyl, 2-methylcyclopentyl,    3-methylcyclopentyl, cis-2,4-dimethylcyclopentyl,    trans-2,4-dimethylcyclopentyl 2,2,4,4-tetramethylcyclopentyl,    2-methylcyclohexyl, 3-methylcyclohexyl, 4-methylcyclohexyl,    cis-2,5-dimethylcyclohexyl, trans-2,5-dimethylcyclohexyl,    2,2,5,5-tetramethylcyclohexyl, 2-methoxycyclopentyl,    2-methoxycyclohexyl, 3-methoxycyclopentyl, 3-methoxycyclohexyl,    2-chlorocyclopentyl, 3-chlorocyclopentyl, 2,4-dichlorocyclopentyl,    2,2,4,4-tetrachlorocyclopentyl, 2-chlorocyclohexyl,    3-chlorocyclohexyl, 4-chlorocyclohexyl, 2,5-dichlorocyclohexyl,    2,2,5,5-tetrachlorocyclohexyl, 2-thiomethylcyclopentyl,    2-thiomethylcyclohexyl, 3-thiomethylcyclopentyl or    3-thiomethylcyclohexyl;-   C₇-C₁₃-aralkyl, preferably C₇- to C₁₂-phenylalkyl, such as benzyl,    1-phenethyl, 2-phenethyl, 1-phenylpropyl, 2-phenylpropyl,    3-phenylpropyl, neophyl(1-methyl-1-phenylethyl), 1-phenylbutyl,    2-phenylbutyl, 3-phenylbutyl or 4-phenylbutyl, particularly    preferably benzyl;-   C₆-C₁₄-aryl, such as phenyl, 1-naphthyl, 2-naphthyl, 1-anthryl,    2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl,    4-phenanthryl or 9-phenanthryl, preferably phenyl, 1-naphthyl or    2-naphthyl, particularly preferably phenyl, unsubstituted or    substituted by one or more    -   C₁-C₁₂-alkyl groups, such as methyl, ethyl, n-propyl, isopropyl,        n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl,        sec-pentyl, neopentyl, 1,2-dimethylpropyl, isoamyl, n-hexyl,        isohexyl, sec-hexyl, n-heptyl, isoheptyl, n-octyl, n-nonyl,        n-decyl or n-dodecyl; preferably C₁-C₆-alkyl, such as methyl,        ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,        tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl,        1,2-dimethylpropyl, isoamyl, n-hexyl, isohexyl, sec-hexyl,        particularly preferably C₁-C₄-alkyl, such as methyl, ethyl,        n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl;    -   halogens, such as fluorine, chlorine, bromine or iodine,        preferably chlorine or bromine;    -   C₁-C₁₂-alkoxy groups, preferably C₁-C₆-alkoxy groups, such as        methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy,        sec-butoxy, tert-butoxy, n-pentyloxy, isopentyloxy, n-hexyloxy        or isohexyloxy, particularly preferably methoxy, ethoxy,        n-propoxy or n-butoxy.

In a particular embodiment, R²⁶ and R²⁷ or R²⁶ and R²⁸ are covalentlybonded to one another with formation of a 4- to 13-membered ring. Forexample, R²⁶ and R²⁷ together may be: —(CH₂)₄—, —(CH₂)₅—, —(CH₂)₆,—(CH₂)₇—, —CH(CH₃)—CH₂—CH₂—CH(CH₃)— or —CH(CH₃)—CH₂—CH₂—CH₂—CH(CH₃)—.

R²⁶ and R²⁷ are each particularly preferably hydrogen, and R²⁸ ismethyl.

The reactions under the conditions described above usually take placewith formation of mixtures which are difficult to separate and whoseproducts result from dimerizations, oligomerizations (from 3 to 8 units)and polymerization (9 or more units) of the aldehyde of formula D.1, andfurthermore form aldol addition reactions, possibly followed, forexample, by elimination of water (dehydration), oxidations orintramolecular crosslinking. During the storage of the novel tanningagents, byproducts resulting from the storage may furthermore occur, forexample due to elimination of water (dehydration), oxidation ordimerization, oligomerization or polymerization or due to crosslinking.

It is possible to isolate individual products of the reactions describedabove and to use them as tanning agents. However, a preferred aspect ofthe present invention is the use of the reaction products onlyincompletely purified or not further purified at all as tanning agentsin process step D) of the novel process.

The tanning agents used according to the invention can be employed forthe pretannning, tanning and retanning of animal hides.

According to the invention, pretreated hides of animals, for examplecattle, pigs, goats or deer, are used as starting materials in processstep D) of the novel process.

Process step D) of the novel process is generally carried out by addingone or more novel tanning agents in one portion or in a plurality ofportions immediately before or during the tanning step. The noveltanning process is preferably carried out at pH of from 2.5 to 4, itfrequently being observed that the pH increases by about 0.3 to threeunits while the novel tanning process is being carried out. The pH canalso be increased by adding agents for increasing the basicity.

Process step D) of the novel process is carried out in general at from10 to 45° C., preferably from 20 to 30° C. A duration of from 10 minutesto 12 hours, preferably from one to three hours, has proven useful. Thenovel tanning process can be carried out in any desired vesselscustomary in tanning, for example by drumming.

In one variant of process step D) of the novel process, the noveltanning agents are used together with one or more conventional tanningagents, for example with chrome tanning agents, mineral tanning agents,syntans, polymer tanning agents or vegetable tanning agents, asdescribed, for example, in Ullmann's Encyclopedia of IndustrialChemistry, Volume A15, pages 259 to 282 and in particular page 268 etseq., 5th edition (1990), Verlag Chemie Weinheim. The weight ratio ofnovel tanning agent to conventional tanning agent or the sum of theconventional tanning agents is expediently from 0.01:1 to 100:1. In anadvantageous variant of the novel process, only a few ppm of theconventional tanning agents are added to the novel tanning agents.However, it is particularly advantageous completely to dispense with theadmixing of conventional tanning agents.

In one variant of process step D) of the novel process, one or moretanning agents described above are added in one portion or in aplurality of portions before or during the pretanning, in a particularlypreferred variant during pickling itself.

In a further variant of process step D) of the novel process, one ormore tanning agents described above are added in one portion or in aplurality of portions before or during one or more retanning steps. Thisvariant of process step D) of the novel process can be carried out underotherwise conventional conditions. Expediently, one or more, i.e. from 2to 6, treatment steps are chosen and washing with water can be effectedbetween treatment steps. The temperature during the individual treatmentsteps is in each case from 5 to 60° C., preferably from 20 to 45° C.Further agents usually used during the retanning are expedientlyemployed, for example fatliquor, polymer tanning agents and acrylate-and/or methacrylate-based fatliquoring agents, retanning reagents basedon resin and vegetable tanning agents, fillers, leather dyes oremulsifiers.

In a special embodiment of process step D) of the novel process, thetanning agents described above are used in the form of pulverulentactive ingredients. Such pulverulent active ingredients contain

-   from 10 to 100, preferably from 40 to 90, % by weight of one or more    tanning agents described above-   and from 0 to 90, preferably from 10 to 60, % by weight of one or    more additives.

The additives are as a rule solid particulate substances. They arepreferably chosen from starch, silica, for example in the form of silicagel, in particular spheroidal silica gels, sheet silicates, alumina andmixed oxides of silicon and aluminum.

Further additives are one or more conventional tanning agents orretanning agents, in particular resin tanning agents, for example theresin tanning agent sold under the name Relugan® D, Tamol® M andBasyntan® DLX by BASF Aktiengesellschaft. Ligninsulfonates are alsosuitable additives.

Typical of the pulverulent active ingredients is furthermore that theyconsist of fine particles having a mean particle diameter of from 100 nmto 0.1 mm. The particle diameters follow a particle diameterdistribution which may be narrow or broad. Bimodal particledistributions are also conceivable. The particles themselves may have anirregular or spherical shape, spherical particle shapes being preferred.The novel pulverulent active ingredients can be metered underparticularly hygienic conditions in the novel tanning process orretanning process.

The pulverulent active ingredients are prepared, for example, asfollows: tanning agents described above which are present in solution,in suspension or in emulsion or in isolated form are used as startingmaterials. Reaction solutions as obtained in the preparation processdescribed above are particularly preferably used as starting materials.

It has proven useful first to concentrate the reaction solutions to aresidual solvent content of 50% by weight or less.

The resulting liquid, solid or oily concentrated reaction solutions arethen sprayed in a spray dryer, preferably in a spray tower. Spray dryersare known to a person skilled in the art and are described, for example,in Vauck/Müller, Grundoperationen chemischer Verfahrenstechnik, VCHWeinheim, 1988, 7th edition, pages 638-740 and pages 765-766, and in theliterature cited therein.

In a preferred embodiment, the novel process for the production ofleather comprises at least the process steps A) and B).

In a further preferred embodiment, the novel process for the productionof leather comprises at least the process steps A), B) and C).

A further preferred embodiment of the novel process for the productionof leather comprises the process steps A) to D).

A particularly advantageous development of the novel process and itsabovementioned preferred embodiments is obtained if, in process step A),at least step (a), i.e. the addition of one or more polyelectrolytes andfrom 0 to 1.5% by weight, based on the salted weight, of lime, isincluded immediately before or during liming.

As mentioned further above in the statements of process step A), thesubstantial saving of lime can be effected in comparison with theconventional procedure on addition of polyelectrolytes.

In the novel process and its preferred embodiments, no lime (0% byweight of lime) is therefore used in a particularly preferred variant instep (a) of process step A) (in this context, deliming in theconventional sense is then no longer necessary).

In combination with the use of compounds of the formula B.1, processwastewaters which have a substantially reduced content of inorganicsalts compared with conventional wastewaters are therefore obtained.There are also indications that at least a part of the polyelectrolytesand the compounds B.1 is incorporated into the leather, whichcontributes further toward reducing the water pollution. Moreover, thestructure of the leather is also advantageously influenced by thisincorporation.

After the hairs have been separated off (in the case of hair-preservingliming), the proteins are precipitated, as a rule with addition ofrelatively strong acids, for example sulfuric acid or formic acid. Inthe case of hair-destroying liming, the removal of the hairs is omittedand the protein content of the wastewaters in this case is of coursehigher. The acidified process wastewater substantially freed fromorganic substances is therefore available for other process steps, butalso for the presoaking and main soaking of fresh rawhides which, forstabilization, have generally being treated with salt prior to delivery.Depending on the desired use, it may be necessary also to adjust the pH.

A particularly advantageous process sequence claimed within the scope ofthe present invention, also with respect to the abovementioned preferredembodiments of the novel process, is accordingly distinguished by thefact that the process wastewater obtained after combination of processstep A) (a) and process step B), i.e. after liming, and substantiallyfreed from the organic components, in particular from proteins and anyhairs, is at least partly used in at least one further process step ofthe process steps A) (b) to A) (d), C) and D) for the production ofleather and/or for the presoaking and main soaking of the freshrawhides.

The present invention therefore furthermore relates to those processwastewaters substantially freed from organic components, in particularfrom proteins or any hairs, which are obtainable after combination ofprocess step A) (a) and process step B), i.e. after liming, according tothe novel process for the production of leather.

As a result of the procedure described above, not only are processwastewaters which have to be disposed of in an expensive manner in theconventional beamhouse eliminated, but the acidified novel processwastewaters can be further used as dilute acids in further processsteps.

The novel process wastewater is preferably used at least partly in step(b) of process step A) and/or in process step D) and/or for thepresoaking and main soaking of the rawhides, particularly preferably inprocess step A) (b) and D) and for the presoaking and main soaking ofthe rawhides.

The present invention furthermore relates to leathers which have beenproduced by the novel process and its preferred embodiments.

The working examples below illustrate the invention.

WORKING EXAMPLES

The values in % by weight are based in each case on the salted weight ofthe hide, unless stated otherwise.

General Working Methods:

1. Leather Production with Hair-Destroying Liming

1.1. Conventional Procedure V1

1.1.1. Soaking

100% by weight, based on the salted weight, of a South German cattlehide were first presoaked at 28° C. with 200% by weight of water and0.2% by weight of Eusapon® W (detergent formulation based on oxo alcoholalkoxylates; BASF Aktiengesellschaft) for 120 minutes in a drum withgentle movement. The liquor was discharged (C1-1 Liquor for standardpresoaking, 200% by weight) and soaking was then effected with 100% byweight of water, 0.2% by weight of Eusapon® W and 0.5% by weight ofsodium carbonate with gentle movement for 15 hours. The liquor was thendischarged (C1-2 Liquor for standard main soaking, 100% by weight).

1.1.2. Liming

For comparative example C1, 100% by weight, based on the salted weight,of a hide were treated in a rotatable 10 l drum with internal baffles insuccession with 80% by weight of water and 1.0% by weight of Mollescal®LS (unhairing agent based on mercaptoethanol; BASF Aktiengesellschaft).After 30 minutes, 0.8% by weight of NaSH (70% strength) and 1% by weightof lime were added and left for a further 30 minutes. 0.75% by weight ofsodium sulfide (60%) and 0.75% by weight of sodium sulfide together with1.0% by weight of lime followed at an interval of 30 minutes. The drumwas operated for a further 30 minutes at 15 revolutions/minute. Afurther 70% by weight of water, 1.0% by weight of lime and 0.04% byweight of Mollescal® AGN (polymeric liming assistant; BASFAktiengesellschaft) were then metered. After 15 hours at from 23 to 27°C. and drum revolutions of in each case 5 minutes per hour at 3revolutions/minute, the experiments were terminated by discharging theliquor (sample C1-3 Liquor for standard liming, 150% by weight) andwashing the pelts once for 15 minutes with 150% by weight of water(sample C1-4 Wash liquor for standard liming, 150% by weight).

Before the further processing, the hides were fleshed and split (2.8mm).

The times stated in the tables below are to be understood as meaningtime intervals relative to the abovementioned product addition(s). If aplurality of products are added at a time, a time is stated only for theproduct mentioned last in the relevant block of the table and added atthis time. If data on the dilution of a product are given, the statedpercentages by weight are based on the undiluted product. The dilutionwas effected in each case with the water before the addition of theproduct. “Diluted 1:3” means, for example, that 1 part by weight of the(undiluted) product was diluted with 3 parts by weight of water.

1.1.3. Deliming

Below, the data in % by weight are based on the pelt weight, grain split2.8 mm (corresponding to 75% salted weight), unless stated otherwise.The deliming was carried out at from 25 to 32° C.: Experi- % by Timement wt. Product pH [min] C1 150 Water, 2× 20 Discharge liquor(C1-5/C1-6 Deliming wash liquor, 300% by weight) 100 Water 8.6 20 0.2Decaltal ®ES-N (pH-regulating deliming agent based on organic esters;BASF Aktiengesellschaft) 0.2 Eusapon ®S (diluted 1:3; detergentformulation based on oxo alcohol alkxoylates; BASF Aktiengesellschaft)0.2 Sodium bisulfite Discharge liquor (C1-7 Deliming liquor, 100% byweight) 50 Water 8.0 45 1.0 Decaltal ®ES-N 1.0 Basozym ®CM (enzymaticbating agent; 45 BASF Aktiengesellschaft) Discharge liquor (C1-8 Batingliquor, 50% by weight) 150 Water 10 Discharge liquor (C1-9 Bating washliquor, 150% by weight)

The penetration of the neutralization over the hide cross section waschecked with phenolphthalein as indicator. The time required for thispurpose was noted.

1.1.4. Pickling and Tanning

Below, the data in % by weight are based on the pelt weight of the hide,grain split 2.8 mm (corresponding to 75% salted weight), unless statedotherwise. Experi- % by Time ment wt. Product pH [min] C1 40 Water 10 6Sodium chloride (8° Be) 1.0 Lipoderm ®fatliquor A1 (fatliquoring 20agent based on natural oils; BASF Aktiengesellschaft; diluted 1:3) 0.4Formic acid (100% strength) (diluted 30 1:5) 0.8 Sulfuric acid (98%strength) 3.0 90 2.5 Relugan ®GTP (modified glutaraldehyde; 3.0 90 BASFAktiengesellschaft; diluted 1:3) 3.0 Basyntan ®SW liquid (sulfone-based3.9 900 tanning agent; BASF Aktiengesellschaft; diluted 1:2) 2.0Tamol ®NA (pH-regulating tanning assistant; BASF Aktiengesellschaft) 0.2Sodium formate 0.2 Sodium formate 4.0 90 0.2 Sodium bicarbonate 0.2Cortymol ®FUN (fungicide; BASF 30 Aktiengesellschaft; diluted 1:3)Discharge liquor (C1-10 Tanning liquor, 40% by weight)1.2. Novel Procedures N1 to N51.2.1. Soaking

100% by weight, based on the salted weight, of a South German cattlehide were first presoaked at 28° C. with 200% by weight of water and0.2% by weight of a branched C₁₀-alcohol alkoxylate having 2 propyleneoxide and 6 ethylene oxide units (surfactant 12; surfactant according toexperiment 12 in table 2 of the prior German Patent Application 101 34441.4) for 120 minutes in a drum with gentle movement. The liquor wasdischarged (NX-1 Presoaking liquor, 200% by weight; X=1, 2, 3, 4 or 5)and soaking was then effected with 100% by weight of water, 0.2% byweight of surfactant 12 and 0.5% by weight of sodium carbonate withgentle movement for 15 hours. The liquor was then discharged (NX-2 Mainsoaking liquor, 100% by weight; X=1, 2, 3, 4 or 5).

1.2.2. Liming

For the novel procedures N1 to N5, 100% by weight, based on the saltedweight, of a hide were treated in a rotatable 10 l drum with internalbaffles in succession with 50% by weight of water and as follows:Experi- % by Time ment wt. Product pH [min] N1 2.5 PE 11(polyethylenimine; 10.5 P oly e lectrolyte according to example 11 intable 1 of the prior German Patent Application 102 11 670.9) 1.5 DTT(100%; racemic dithiothreitol; 9.7 60 Biosynth Aktiengesellschaft) 1.5Sodium hydroxide (50% strength 10.7 30 aqueous solution) 1.5 Sodiumhydroxide (50% strength 12.4 60 aqueous solution) 50 Water 12.4 900Discharge liquor (N1-3 Liming liquor, 100% by weight) 150 Water 10Discharge liquor (N1-4 Liming wash liquor, 150% by weight)

Experi- % by Time ment wt. Product pH [min] N2 1.0 Waterglass (50%strength aqueous 9.7 60 solution) 1.5 DTT (100%) 9.7 60 1.5 Sodiumhydroxide (50% strength 10.7 30 aqueous solution) 1.5 Sodium hydroxide(50% strength 12.4 60 aqueous solution) 50 Water 12.4 900 Dischargeliquor (N2-3 Liming liquor, 100% by weight) 150 Water 10 Dischargeliquor (N2-4 Liming wash liquor, 150% by weight)

Experi- % by Time ment wt. Product pH [min] N3 1.0 PE 8 (acrylic acid(AA)/maleic 60 anhydride (MAA) copolymer, molar AA:MAA ratio = 8:2;polyelectrolyte according to example 8 in table 1 of the prior GermanPatent Application 102 11 670.9) 0.75 DTT (100%) 60 0.5 Urea 1.5 Sodiumhydroxide (50% strength 10.7 30 aqueous solution) 1.5 Sodium hydroxide(50% strength 12.4 60 aqueous solution) 50 Water 12.4 900 Dischargeliquor (N3-3 Liming liquor, 100% by weight) 150 Water 10 Dischargeliquor (N3-4 Liming wash liquor, 150% by weight)

Experi- % by Time ment wt. Product pH [min] N4 0.5 Mollescal ®MF(unhairing agent based 60 on thioglycolic acid; BASF Aktiengesellschaft)0.5 PE 14 (cationic starch; polyelectrolyte according to example 14 intable 1 of the prior German Patent Application 102 11 670.9) 1.0 DTT(100%) 2.0 Sodium hydroxide (50% strength 12.1 30 aqueous solution) 0.4Sodium hydroxide (50% strength 60 aqueous solution) 50 Water 12.4 900Discharge liquor (N3-4 Liming liquor, 100% by weight) 150 Water 10Discharge liquor (N4-4 Liming wash liquor, 150% by weight)

Experi- % by Time ment wt. Product pH [min] N5 1.0 Basozym ®L10(enzymatic bating 60 assistant; BASF Aktiengesellschaft) 1.5 DTT (100%)2.0 Sodium hydroxide (50% strength 30 aqueous solution) 0.4 Sodiumhydroxide (50% strength 60 aqueous solution) 50 Water 12.4 900 Dischargeliquor (N5-3 Liming liquor, 100% by weight) 150 Water 10 Dischargeliquor (N5-4 Liming wash liquor, 150% by weight)

Before the further processing, the hides were fleshed and split (2.8mm).

1.2.3. Deliming

Below, the data in % by weight are based on the pelt weight, grain split2.8 mm (corresponding to 75% salted weight), unless stated otherwise.The deliming was carried out at from 25 to 32° C.: Experi- % by Timement wt. Product pH [min] N1 50 Water 20 0.2 Decaltal ®ES-N 8.6 20 0.2Surfactant 12 (diluted 1:3) Discharge liquor (N1-5 Deliming liquor, 50%by weight) 50 Water 8.0 45 1.0 Decaltal ®ES-N 1.0 Basozym ®CM 45Discharge liquor (N1-6 Bating liquor, 50% by weight) 150 Water 10Discharge liquor (N1-7 Bating wash liquor, 150% by weight)

Experi- % by Time ment wt. Product pH [min] N2 50 Water 20 0.2Decaltal ®ES-N 8.6 20 0.2 Surfactant 11 (surfactant according toexperiment 11 in table 2 of the prior German Patent Application 101 34441.4; diluted 1:3) Discharge liquor (N2-5 Deliming liquor, 50% byweight) 50 Water 8.0 45 1.0 Decaltal ®ES-N 1.0 Basozym ®CM 45 Dischargeliquor (N2-6 Bating liquor, 50% by weight) 150 Water 10 Discharge liquor(N2-7 Bating wash liquor, 150% by weight)

Experi- % by Time ment wt. Product pH [min] N3 50 Water 20 0.2Decaltal ®ES-N 8.6 20 0.2 Surfactant 20 (surfactant according toexperiment 20 in table 2 of the prior German Patent Application 101 34441.4; diluted 1:3) Discharge liquor (N3-5 Deliming liquor, 50% byweight) 50 Water 8.0 45 1.0 Decaltal ®ES-N 1.0 Basozym ®CM 45 Dischargeliquor (N3-6 Bating liquor, 50% by weight) 150 Water 10 Discharge liquor(N3-7 Bating wash liquor, 150% by weight)

Experi- % by Time ment wt. Product pH [min] N4 50 Water 20 0.2Decaltal ®ES-N 8.6 20 0.2 Surfactant 12 (diluted 1:3) Discharge liquor(N4-5 Deliming liquor, 50% by weight) 50 Water 8.0 45 1.0 Decaltal ®ES-N1.0 Basozym ®CM 45 Discharge liquor (N4-6 Bating liquor, 50% by weight)150 Water 10 Discharge liquor (N4-7 Bating wash liquor, 150% by weight)

Experi- % by Time ment wt. Product pH [min] N5 50 Water 20 0.2Decaltal ®ES-N 8.6 20 0.2 Surfactant 12 (diluted 1:3) Discharge liquor(N5-5 Deliming liquor, 50% by weight). 50 Water 8.0 45 1.0Decaltal ®ES-N 1.0 Basozym ®CM 45 Discharge liquor (N5-6 Bating liquor,50% by weight) 150 Water 10 Discharge liquor (N5-7 Bating wash liquor,150% by weight)

The penetration of the neutralization over the hide cross section waschecked with phenolphthalein as an indicator. The time required for thispurpose was noted.

1.2.4. Pickling and Tanning

Below, the data in % by weight are based on the pelt weight, grain split2.8 mm (corresponding to 75% salted weight), unless stated otherwise.Experi- % by Time ment wt. Product pH [min] N1 40 Water 10 0.5 PE 11 1.0Lipoderm ®fatliquor A1 (diluted 1:3) 20 0.4 Formic acid (100% strength)(diluted 30 1:5) 0.8 Sulfuric acid (98% strength) 2.9 90 1.8 TA 1 ( tanning a gent according to 3.4 90 example 1.1 of the prior German PatentApplication 102 31 293.1) 3.0 Basyntan ®SW liquid (diluted 1:2) 4.2 9002.0 Tamol ®NA 1.0 Sodium formate 4.0 90 0.2 Sodium bicarbonate 0.2Cortymol ® FUN (diluted 1:3) 30 Discharge liquor (N1-8 Tanning liquor,40% by weight)

Experi- % by Time ment wt. Product pH [min] N2 40 Water 10 1.0Waterglass (50% strength aqueous solution) 1.0 Lipoderm ®fatliquoring A1(diluted 20 1:3) 0.4 Formic acid (100% strength) (diluted 30 1:5) 0.8Sulfuric acid (98% strength) 2.9 90 1.8 TA 4 ( t anning a gent accordingto 3.4 90 example 1.4 of the prior German Patent Application 102 31293.1) 3.0 Basyntan ®SW liquid (diluted 1:2) 4.2 900 2.0 Tamol ®NA 1.0Sodium formate 4.0 90 0.2 Sodium bicarbonate 0.2 Cortymol ®FUN (diluted1:3) 30 Discharge liquor (N2-8 Tanning liquor, 40% by weight)

Experi- % by Time ment wt. Product pH [min] N3 40 Water 10 2.5 PE 8 1.0Lipoderm ® fatliquor A1 (diluted 1:3) 20 0.4 Formic acid (100% strength)(diluted 30 1:5) 0.8 Sulfuric acid (98% strength) 2.9 90 1.8 TA 3 ( tanning a gent according to 3.4 90 example 1.3 of the prior German PatentApplication 102 31 293.1) 3.0 Basyntan ®SW liquid (diluted 1:2) 4.2 9002.0 Tamol ®NA 1.0 Sodium formate 4.0 90 0.2 Sodium bicarbonate 0.2Cortymol ®FUN (diluted 1:3) 30 Discharge liquor (N1-8 Tanning liquor,40% by weight)

Experi- % by Time ment wt. Product pH [min] N4 40 Water 10 2.0 PE 4(polyacrylate sodium salt; polyelectrolyte according to example 4 intable 1 of the prior German Patent Application 102 11 670.9) 1.0Lipoderm ® fatliquor A1 (diluted 1:3) 20 0.4 Formic acid (100% strength)(diluted 30 1:5) 0.8 Sulfuric acid (98% strength) 2.9 90 1.8 TA 2 ( tanning a gent according to 3.4 90 example 1.2 of the prior German PatentApplication 102 31 293.1) 3.0 Basyntan ®SW liquid (diluted 1:2) 4.2 9002.0 Tamol ®NA 1.0 Sodium formate 4.0 90 0.2 Sodium bicarbonate 0.2Cortymol ®FUN (diluted 1:3) 30 Discharge liquor (N1-8 Tanning liquor,40% by weight)

Experi- % by Time ment wt. Product pH [min] N5 40 Water 10 2.0 PE 7(polymethacrylic acid; polyelectrolyte according to example 7 in table 1of the prior German Patent Application 102 11 670.9) 1.0 Lipoderm ®fatliquor A1 (diluted 1:3) 20 0.4 Formic acid (100% strength) (diluted30 1:5) 0.8 Sulfuric acid (98% strength) 2.9 90 1.8 TA 1 3.4 90 3.0Basyntan ®SW liquid (diluted 1:2) 4.2 900 2.0 Tamol ®NA 1.0 Sodiumformate 4.0 90 0.2 Sodium bicarbonate 0.2 Cortymol ®FUN (diluted 1:3) 30Discharge liquor (N1-8 Tanning liquor, 40% by weight)1.3. Novel Procedures N6 and N7 with Working-Up and Recycling of theLiquors1.3.1. Soaking

100% by weight, based on the salted weight, of a South German cattlehide were first presoaked at 28° C. with 200% by weight of aqueous,purified liquor (NX-C; X=1, 2, 3, 4 or 5) and 0.1% by weight ofsurfactant 12 for 120 minutes in a drum with gentle movement. The liquorwas discharged (NX-1 Presoaking liquor, 200% by weight) and then soakingwas effected with a further 100% by weight of aqueous, purified liquor(NX-C), 0.1% by weight of surfactant 12 and 0.5% by weight of sodiumcarbonate with occasional movement for 15 hours. The liquor was thendischarged (NX-2 Main soaking liquor, 100% by weight).

1.3.2. Liming

For the novel examples N6 to N7, 100% by weight, based on the saltedweight, were treated in a rotatable 10 l drum with internal baffles insuccession with 50% by weight of water and as follows: Experi- % by Timement wt. Product pH [min] N6 2.5 PE 11 10.5 (cf. 1.5 DTT (100%) 9.7 60N1) 1.5 Sodium hydroxide (50% strength 10.7 30 aqueous solution) 1.5Sodium hydroxide (50% strength 12.4 60 aqueous solution) 50 Water 12.4900 Discharge liquor (N6-3 Liming liquor, 100% by weight) 150 Water 10Discharge liquor (N6-4 Liming wash liquor, 150% by weight)

Experi- % by Time ment wt. Product pH [min] N7 1.0 Waterglass (50%strength aqueous 9.7 60 (cf. solution) N2) 1.5 DTT (100%) 9.7 60 1.5Sodium hydroxide (50% strength 10.7 30 aqueous solution) 1.5 Sodiumhydroxide (50% strength 12.4 60 aqueous solution) 50 Water 12.4 900Discharge liquor (N7-3 Liming liquor, 100% by weight) 150 Water 10Discharge liquor (N7-4 Liming wash liquor, 150% by weight)

Before the further processing, the hides were fleshed and split (2.8mm).

The liquors NX-3 and NX-4 (X=6 and 7, respectively) were combined (250%)and brought to pH 4.5 with concentrated sulfuric acid (technical-grade,98%). The precipitated protein was separated off using a chamber filterpress. The data of the combined and purified liquors NX-3 and NX-4 areshown below under point 1.8 Summary of the results with hair-destroyingliming (liquor NX-A, 250%; X=6 and 7, respectively).

1.3.3. Deliming

Below, the data in % by weight are based on the pelt weight, grain split2.8 mm (corresponding to 75% salted weight), unless stated otherwise.The deliming was carried out at from 25 to 32° C.: Experi- % by Timement wt Product pH [min] N6 50 Aqueous, purified liquor (NX-A) 20 (Cf.N1) 0.2 Decaltal ®ES-N 8.6 20 0.1 Surfactant 12 (diluted 1:3) Dischargeliquor (N6-5 Deliming liquor, 50% by weight) 50 Water 8.0 45 1.0Decaltal ®ES-N 1.0 Basozym ®CM 45 Discharge liquor (N6-6 Bating liquor,50% by weight) 150 Water 10 Discharge liquor (N6-7 Bating wash liquor,150% by weight)

Experi- % by Time ment wt. Product pH [min] N7 50 Aqueous, purifiedliquor (NX-A) 20 (cf. N2) 0.2 Decaltal ®ES-N 8.6 20 0.1 Surfactant 11(diluted 1:3) Discharge liquor (N7-5 Deliming liquor, 50% by weight) 50Water 8.0 45 1.0 Decaltal ®ES-N 1.0 Basozym ®CM 45 Discharge liquor(N7-6 Bating liquor, 50% by weight) 150 Water 10 Discharge liquor (N7-7Bating wash liquor, 150% by weight)

The penetration of the neutralization over the hide cross section waschecked with phenolphthalein as an indicator. The time required for thispurpose was noted.

The combined liquors NX-5, NX-6 and NX-7 give liquor NX-B (250%, pH 8;X=1, 2, 3, 4 or 5)

1.3.4. Pickling and Tanning

Below, the data in % by weight are based on the pelt weight, grain split2.8 mm (corresponding to 75% salted weight), unless stated otherwise.Experi- % by Time ment wt. Product pH [min] N6 40 Aqueous, purifiedliquor (NX-A) 10 (cf. 0.5 PE 11 N1) 1.0 Lipoderm ® fatliquor A1 (diluted1:3) 20 0.4 Formic acid (100% strength) (diluted 30 1:5) 0.8 Sulfuricacid (98% strength) 2.9 90 1.8 TA 1 3.4 90 3.0 Basyntan ®SW liquid(diluted 1:2) 4.2 900 2.0 Tamol ®NA 1.0 Sodium formate 4.0 90 0.2 Sodiumbicarbonate 0.2 Cortymol ®FUN (diluted 1:3) 30 Discharge liquor (N6-8Tanning liquor, 40% by weight)

Experi- % by Time ment wt. Product pH [min] E7 40 Aqueous, purifiedliquor (NX-A) 10 (cf. 1.0 Waterglass (50% strength aqueous N2) solution)1.0 Lipoderm ® fatliquor A1 (diluted 1:3) 20 0.4 Formic acid (100%strength) (diluted 30 1:5) 0.8 Sulfuric acid (98% strength) 2.9 90 1.8TA 4 3.4 90 3.0 Basyntan ®SW liquid (diluted 1:2) 4.2 900 2.0 Tamol ®NA1.0 Sodium formate 4.0 90 0.2 Sodium bicarbonate 0.2 Cortymol ®FUN(diluted 1:3) 30 Discharge liquor (N7-8 Tanning liquor, 40% by weight)

The remainder of the liquor NX-A (182%, based on salted weight, pH 4.5)and 118% of the liquor NX-B (based on salted weight, pH 8) were combinedto give liquor NX-C (300%, based on salted weight, pH 6.5).

NX-8 (30%, based on salted weight, pH 4.5) and 71% of liquor NX-B (basedon salted weight, pH 8) were disposed of.

1.4. Assessment of the Conventional Procedure C1 and of the NovelProcedures N1 to N7 According to Liming and the Corresponding ResidualLiquors

The pelts obtained by the novel procedure are equivalent with regard toswelling to those obtained by the conventional procedure but aredistinguished by a smoother and flatter grain, in particular those peltsobtained according to N4 to N7. The epidermis and the hairs with hairroots have been completely removed.

The residual liquors of the novel procedures can be acidified to pH 4.5with organic or, preferably, inorganic acids, e.g. sulfuric acid,without evolution of hydrogen sulfide, and the precipitated proteins canbe separated off without problems by filtration. The residual liquorstreated in this manner are generally clear.

1.5. Further Processing of Comparative Example C1 and of Novel ExamplesN1 to N7 in the Retanning

In the case of comparative example C1 and of the novel example N1, theprocedure was based on the data in the table shown below. The furtherprocessing of the novel examples N2 to N7 was carried out in ananalogous manner.

Lipoderm® fatliquor LA (natural lecithin-based fatliquoring agent),Lipoderm® fatliquor FP (polymer fatliquoring agent), Lipoderm® Oil SK(sulfochlorinated liquid paraffin), Relugan® RV (polymer tanning agent),Basyntan® DLX-N (synthetic sulfone-based tanning agent) and Luganil®olive brown N (leather dye) are commercial products of BASFAktiengesellschaft; Tara-Granofin® TA (natural tanning agent) is acommercial product of Clariant AG. The sources of the other commercialproducts have been mentioned elsewhere. % by Temp. pH Time wt. Product(° C.) N1 C1 [min] 150 Water 30 10 4.0 Basyntan ®SW 30 1.5 Tamol ®NA 5.45.0 20 0.3 Sodium bicarbonate 1.5 Lipoderm ®Licker A1 60 5.4 5.0 30 1.0Lipoderm ®fat liquor LA Discharge liquor (C1-11 Neutralization liquor;NX-9 Neutralization liquor) 150 Water 30 10 Discharge liquor, (C1-12Neutralization wash liquor; NX-10 Neutralization wash liquor) 70 Water30 15 3.0 Relugan ®RV 10.0 Basyntan ®SW 5.0 4.8 30 8.0 Tara-Granofin ®TA4.0 Basyntan ®DLX-N 2.0 Tamol ®NA 5.4 5.1 10 0.5 Sodium bicarbonate 2.0Luganil ®olive brown N complete 120 penetra- tion of dye 0.5 Formic acid(100%) (diluted 15 1:10) Discharge liquor, (C1-13 Retanning liquor;NX-11 Retanning liquor) 200 Water 60 15 3.0 Lipoderm ® fatliquor FP(diluted 1:3) 6.0 Lipoderm ® fatliquor A1 60 60 2.0 Lipoderm ® fatliquorLA 2.0 Lipoderm ® Oil SK (mixed and diluted 1:7) 0.1 Formic acid (100%)(diluted 15 1:10) 0.1 Formic acid (100%) (diluted 20 1:10) 0.05 Formicacid (100%) (diluted 3.1 3.1 15 1:10) Discharge liquor (C1-14Fatliquoring liquor; NX-12 Fatliquoring liquor) 200 Water 50 20Discharge liquor (C1-15 Fatliquoring wash liquor; NX-13 Fatliquoringwash liquor) 200 Water 25 15 0.3 Cortymol ®FUN

The leathers thus obtained were sammed and shaved by conventionalmethods. The shaved thickness of the leathers was 2.0-2.2 mm (shavedweight corresponds to 25% of salted weight).

The leathers obtained were worked up in a conventional manner and theirphysical properties and performance characteristics were then tested.

1.6. Assessment of the Crust Leathers Obtained by Conventional ProcedureC1 and Novel Procedures N1 to N7

Apart from the smoother and finer grains of procedures N4 to N7, thecrust leathers produced according to the invention do not differ intheir haptic and optical properties from the conventional crustleathers. Leathers having a very good dyeing and good tight-grainedcharacter in combination with very good body and excellent softness withelegant handle are obtained. Quality of the Stitch tear hair removal,Grain resistance epidermis tightness* according to DIN removal and hideWet white 53331 Procedure pigment removal* leather [N] C1 2 2 140 N1 2 2176 N2 1.5 2 173 N3 1 2 178 N4 1 1 185 N5 1 1 190 N6 2 1 188 N7 1.5 2178*Evaluation by rating1.7. Analysis of the Liquors

All liquor data are based on the salted weight (COD: chemical oxygendemand): Sam- Sulfide COD ple Process pH [ppm]* [mg O₂/l] Liquor C1-1Standard presoaking 1.3 8200 200 liquor C1-2 Standard main soaking 9.52.0 11300 100 liquor C1-3 Standard liming liquor 12.3 1000 48500 150(430) C1-4 Standard liming wash 12.3 310 8900 150 liquor C1-5 Delimingwash liquor 12.0 57 4500 113 C1-6 Deliming wash liquor 11.9 105 2500 113C1-7 Deliming liquor 8.6 73 1600 75 C1-8 Bating liquor 8.0 — 16500 38C1-9 Bating wash liquor 8.0 — 2400 113 C1-10 Tanning liquor 4.0 — 1470030 Total up to tanning 12600 1080 C1-11 Neutralization liquor 5.0 —18000 38 C1-12 Neutralization wash 5.1 — 7150 38 liquor C1-13 Retanningliquor 3.1 — 41500 18 C1-14 Fatliquoring liquor 3.1 — 17000 50 C1-15Fatliquoring wash liquor 3.1 — 5500 50 Total up to crust 12900 1273

Sam- Sulfide COD ple Process pH [ppm]* [mg O₂/l] Liquor N1-1 Presoakingliquor 8.3 2.5 8200 200 N1-2 Main soaking liquor 9.4 2.5 11300 100 N1-3Liming liquor 12.4 74 (6) 72750 100 N1-4 Liming wash liquor 12.4 3615900 150 N1-5 Deliming liquor 8.5 9 1600 38 N1-6 Bating liquor 8.0 —16500 38 N1-7 Bating wash liquor 8.0 — 2400 113 N1-8 Tanning liquor 4.0— 14700 30 Total up to tanning 18000 768 N1-9 Neutralization liquor 5.4— 15000 38 N1-10 Neutralization wash 5.4 — 6300 38 liquor N1-11Retanning liquor 3.1 — 37500 18 N1-12 Fatliquoring liquor 3.1 — 10550 50N1-13 Fatliquoring wash liquor 3.1 — 3950 50 Total up to crust 16700 960N2-1 Presoaking liquor 8.3 2.0 8500 200 N2-2 Main soaking liquor 9.4 2.010900 100 N2-3 Liming liquor 12.4 70 (4) 71500 100 N2-4 Liming washliquor 12.4 33 16300 150 N2-5 Deliming liquor 8.5 7 1800 38 N2-6 Batingliquor 8.0 — 15600 38 N2-7 Bating wash liquor 7.9 — 2200 113 N2-8Tanning liquor 4.0 — 15200 30 Total up to tanning 17900 768 N2-9Neutralization liquor 5.5 — 14800 38 N2-10 Neutralization wash 5.5 —5900 38 liquor N2-11 Retanning liquor 3.0 — 36900 18 N2-12 Fatliquoringliquor 3.0 — 9900 50 N2-13 Fat liquoring wash liquor 3.0 — 4500 50 Totalup to crust 16500 960

Sam- Sulfide COD ple Process pH [ppm]* [mg O₂/l] Liquor N3-1 Presoakingliquor 8.3 2.5 8000 200 N3-2 Main soaking liquor 9.4 2.5 12000 100 N3-3Liming liquor 12.4 65 (5) 73000 100 N3-4 Liming wash liquor 12.4 3715200 150 N3-5 Deliming liquor 8.5 8 1700 38 N3-6 Bating liquor 8.1 —15900 38 N3-7 Bating wash liquor 8.1 — 2300 113 N3-8 Tanning liquor 4.1— 14200 30 Total up to tanning 17900 768 N3-9 Neutralization liquor 5.4— 15600 38 N3-10 Neutralization wash 5.4 — 6500 38 liquor N3-11Retanning liquor 3.0 — 35500 18 N3-12 Fatliquoring liquor 3.0 — 11100 50N3-13 Fatliquoring wash liquor 3.1 — 3700 50 Total up to crust 16600 960

Sam- Sulfide COD ple Process pH [ppm]* [mg O₂/l] Liquor N4-1 Presoakingliquor 8.3 2.5 8100 200 N4-2 Main soaking liquor 9.4 2.5 11500 100 N4-3Liming liquor 12.4 72 (6) 72500 100 N4-4 Liming wash liquor 12.4 3516100 150 N4-5 Deliming liquor 8.5 9 1750 38 N4-6 Bating liquor 7.9 —16300 38 N4-7 Bating wash liquor 8.0 — 2600 113 N4-8 Tanning liquor 4.0— 14100 30 Total up to tanning 18000 768 N4-9 Neutralization liquor 5.3— 14800 38 N4-10 Neutralization wash 5.3 — 6200 38 liquor N4-11Retanning liquor 3.1 — 38000 18 N4-12 Fatliquoring liquor 3.1 — 10900 50N4-13 Fatliquoring wash liquor 3.1 — 4000 50 Total up to crust 16700 960

Sam- Sulfide COD ple Process pH [ppm]* [mg O₂/l] Liquor N5-1 Presoakingliquor 8.3 2.5 8700 200 N5-2 Main soaking liquor 9.4 2.5 11000 100 N5-3Liming liquor 12.4 77 (6) 73000 100 N5-4 Liming wash liquor 12.4 3617000 150 N5-5 Deliming liquor 8.5 9 1500 38 N5-6 Bating liquor 8.2 —15200 38 N5-7 Bating wash liquor 8.2 — 2500 113 N5-8 Tanning liquor 4.0— 14200 30 Total up to tanning 18300 768 N5-9 Neutralization liquor 5.5— 15100 38 N5-10 Neutralization wash 5.5 — 6150 38 liquor N5-11Retanning liquor 3.1 — 37500 18 N5-12 Fatliquoring liquor 3.1 — 10700 50N5-13 Fatliquoring wash liquor 3.1 — 4100 50 Total up to crust 16900 960

Sam- Sulfide COD ple Process pH [ppm]* [mg O₂/l] Liquor N6-1 Presoakingliquor 8.3 2.5 19400 200 N6-2 Main soaking liquor 9.4 2.5 22500 100 N6-3Liming liquor 12.4 74 (6) 72750 100 N6-4 Liming wash liquor 12.4 3615900 150 N6-5 Deliming liquor 8.5 9 14300 38 N6-6 Bating liquor 8.0 —16500 38 N6-7 Bating wash liquor 7.9 — 2400 113 N6-8 Tanning liquor 4.0— 27400 30 Total up to tanning 18300 401 N6-9 Neutralization liquor 5.5— 15000 38 N6-10 Neutralization wash 5.4 — 6300 38 liquor N6-11Retanning liquor 3.0 — 37500 18 N6-12 Fatliquoring liquor 3.1 — 10550 50N6-13 Fatliquoring wash liquor 3.1 — 3950 50 Total up to crust 14200 593

Sam- Sulfide COD ple Process pH [ppm]* [mg O₂/l] Liquor N7-1 Presoakingliquor 8.3 2.0 16000 200 N7-2 Main soaking liquor 9.4 2.0 19100 100 N7-3Liming liquor 12.4 63 (5) 72750 100 N7-4 Liming wash liquor 12.4 3015900 150 N7-5 Deliming liquor 8.5 5 8100 50 N7-6 Bating liquor 8.0 —16500 50 N7-7 Bating wash liquor 8.0 — 2400 150 N7-8 Tanning liquor 4.0— 21200 30 Total up to tanning 14500 401 N7-9 Neutralization liquor 5.4— 15000 38 N7-10 Neutralization wash 5.4 — 6300 38 liquor N7-11Retanning liquor 2.9 — 37500 18 N7-12 Fatliquoring liquor 2.9 — 10550 50N7-13 Fatliquoring wash liquor 2.9 — 3950 50 Total up to crust 10800 593*The sulfide determination was effected in the form of hydrogen sulfideafter acidification of the sample with concentrated hydrochloric acid,heating to 90° C. and stripping. Values stated in brackets relate tosulfide determinations by cold stripping of hydrogen sulfide with buffersolutions at pH 4.Only sulfide present in free form as hydrogen sulfide is detected by thelatter method of determination.1.8. Summary of the Results with Hair-Destroying Liming

Comparison for soaking 1000 kg salted weight: Water Water consumptionconsumption up to up to COD_(total) Experi- tanning tanning COD [kg CODment [m³] [rel. %] [mg O₂/l] O₂/kg] [rel. %] C1 10.80 100 12600 136.2100 N1 7.68 71 18000 138.2 101 N2 7.68 71 17900 137.4 101 N3 7.68 7117900 137.3 101 N4 7.68 71 18000 138.3 102 N5 7.68 71 18300 140.2 103 N64.01 37 18300 73.2 54 N7 4.01 37 14500 58.0 43

Water Water consumption consumption COD_(total) Experi- up to crust upto crust COD [kg COD ment [m³] [rel. %] [mg O₂/l] O₂/kg] [rel. %] C112.73 100 12900 164.1 100 N1 9.60 75 16700 160.0 97 N2 9.60 75 16500158.8 97 N3 9.60 75 16600 159.2 97 N4 9.60 75 16700 160.3 98 N5 9.60 7516900 162.2 99 N6 5.93 47 14200 84.2 51 N7 5.93 47 10800 64.0 39

Protein precipitate from N6 and N7:

-   N6: Yield: 100 kg, dry substance: 30%, COD [mg O₂/kg]: 64 800, ash    content: 1.0%;-   N7: Yield: 125 kg, dry substance: 30%, COD [mg O₂/kg]: 80 300, ash    content: 1.4%

Worked-up and reused liquors from N6 and N7: COD DS Ash [mg LiquorLiquor Process pH [%] [%] O₂/l] [%] N6-A N6-3 + N6-4 (before 12.5 7.80.8 38600 250 precipitation) N6-A N6-3 + N6-4 (after 4.5 5.7 2.6 12700250 precipitation) N6-B N6-5 + N6-6 + E6-7 8 1.7 0.5 7600 189 N6-C N6-A(182%) + N6-B 6.5 4.1 1.2 10700 300 (118%) N6-D N6-1 + N6-2 + N6-B 6.5 —— 18300 401 (71%) + N6-8

COD DS Ash [mg Liquor Liquor Process pH [%] [%] O₂/l] [%] N7-A N7-3 +N7-4 (before 12.5 7.8 0.8 38600 250 precipitation) N7-A N7-3 + N7-4(after 4.5 5.7 2.6 6500 250 precipitation) N7-B N7-5 + N7-6 + N7-7 8 1.70.5 6400 189 N7-C N7-A (182%) + N7-B 6.5 4.1 1.2 6500 300 (118%) N7-DN7-1 + N7-2 + N7-B 6.5 — — 14500 401 (71%) + N7-82. Leather Production with Hair-Preserving Ash2.1. Conventional Procedure V22.1.1. Soaking

100% by weight, based on the salted weight, of a South German cattlehide were first presoaked at 28° C. with 200% by weight of water and0.2% by weight of Eusapon® W for 120 minutes in a drum with gentlemovement. The liquor was discharged (C2-1 Standard presoaking liquor,200% by weight) and soaking was then effected with 100% by weight ofwater, 0.2% by weight of Eusapon® W and 0.5% by weight of sodiumcarbonate with occasional movement for 15 hours. The liquor was thendischarged (C2-2 Standard main soaking liquor, 100% by weight).

2.1.2. Liming

For comparative example C2, 100% by weight, based on the salted weight,were treated in a rotatable 10 l drum with internal baffles insuccession with 60% by weight of water and, in each case after 60minutes, 1.2% by weight of Mollescal MF, 0.8% by weight of lime and 1%by weight of sodium sulfide (60%). This was followed by the beginning offiltration with a duration of 120 minutes. Additions of 1.6% by weightof lime and 40% by weight of water followed at an interval of 60minutes. After 15 hours at from 23 to 27° C. and drum revolutions of ineach case 5 minutes per hour at 3 revolutions/minute, the experimentswere terminated by discharging the liquor (sample C2-3 Standard limingliquor, 100% by weight) and the pelt was washed once for 15 minutes with150% by weight of water (sample C2-4 Standard liming wash liquor, 150%by weight).

Before the further processing, the hides were fleshed and split (2.8mm).

2.1.3. Deliming

Below, the data in % by weight are based on the pelt weight, grain split2.8 mm (corresponding to 75% salted weight), unless stated otherwise.The deliming was carried out at from 25 to 32° C.: Experi- % by Timement wt. Product pH [min] C2 150 Water, 2× 20 Discharge liquor(C2-5/C2-6 Deliming wash liquor, 300% by weight) 100 Water 8.6 20 0.2Decaltal ®ES-N 0.2 Eusapon ® S (diluted 1:3) 0.2 Sodium bisulfiteDischarge liquor (C2-7 Deliming liquor, 100% by weight) 50 Water 8.0 451.0 Decaltal ® ES-N 1.0 Basozym ® CM 45 Discharge liquor (C2-8 Batingliquor, 50% by weight) 150 Water 10 Discharge liquor (C2-9 Bating washliquor, 150% by weight)

The penetration of the neutralization over the hide cross section waschecked with phenolphthalein as an indicator. The time required for thispurpose was noted.

2.1.4. Pickling and Tanning

Below, the data in % by weight are based on the pelt weight, grain split2.8 mm (corresponding to 75% salted weight), unless stated otherwise.Experi- % by Time ment wt. Product pH [min] C2 40 Water 10 6 Sodiumchloride (8° Be) 1.0 Lipoderm fatliquor A1 (diluted 1:3) 20 0.4 Formicacid (100% strength) (diluted 30 1:5) 0.8 Sulfuric acid (98% strength)3.0 90 2.5 Relugan ® GTP (diluted 1:3) 3.0 90 3.0 Basyntan ® SW liquid(diluted 1:2) 3.9 900 2.0 Tamol ® NA 0.2 Sodium formate 0.2 Sodiumformate 4.0 90 0.2 Sodium bicarbonate 0.2 Cortymol ® FUN (diluted 1:3)30 Discharge liquor (C2-10 Tanning liquor, 40% by weight)2.2. Novel Procedure N8 with Working-Up and Recycling of the Liquors2.2.1. Soaking

100% by weight, based on the salted weight, of a South German cattlehide were first presoaked at 28° C. with 200% by weight of aqueous,purified liquor (NX-C) and 0.1% by weight of surfactant 12 for 120minutes in a drum with gentle movement. The liquor was discharged (N8-1Presoaking liquor, 200% by weight) and soaking was then effected with afurther 100% by weight of aqueous, purified liquor (NX-C), 0.1% byweight of surfactant 12 and 0.5% by weight of sodium carbonate withoccasional movement for 15 hours. The liquor was then discharged (N8-2Main soaking liquor, 100% by weight).

2.2.2. Liming

For the novel procedure N8, 100% by weight, based on the salted weight,were treated in a rotatable 10 l drum with internal baffles insuccession with 60% by weight of water and as follows: Experi- % by Timement wt. Product pH [min] N8 2.5 PE 11 10.5 1.0 DTT (100%) 9.7 60 0.8Sodium hydroxide (50% strength 30 aqueous solution) option- Separationof the (lime-free) hairs 120 al from the protein 1.2 Sodium hydroxide(50% strength 30 aqueous solution) 0.4 Sodium hydroxide (50% strength 60aqueous solution) 40 Water 12.4 900 Discharge liquor (N8-3 Limingliquor, 100% by weight) 150 Water 10 Discharge liquor (N8-4 Liming washliquor, 150% by weight)

Before the further processing, the hides were fleshed and split (2.8mm).

The liquors N8-3 and N8-4 were combined (250%) and brought to pH 4.5with concentrated sulfuric acid (technical-grade, 98%). The precipitatedprotein was separated off using a chamber filter press. The data of thecombined and purified liquors N8-3 and N8-4 are shown below under point2.7 Summary of the results with hair-preserving liming (liquor N8-A,250%).

2.2.3. Deliming

Below, the data in % by weight are based on the pelt weight, grain split2.8 mm (corresponding to 75% salted weight), unless stated otherwise.The deliming was carried out at from 25 to 32° C.: Experi- % by Timement wt. Product pH [min] N8 50 Aqueous, purified liquor (N8-A) 20 0.2Decaltal ® ES-N 8.6 20 0.1 Surfactant 12 (diluted 1:3) Discharge liquor(N8-5 Deliming liquor, 50% by weight) 50 Water 1.0 Decaltal ® ES-N 8.045 1.0 Basozym ® CM 45 Discharge liquor (N8-6 Bating liquor, 50% byweight) 150 Water 10 Discharge liquor (N8-7 Bating wash liquor, 150% byweight)

The penetration of the neutralization over the hide cross section waschecked with phenolphthalein as an indicator. The time required for thispurpose was noted.

The combined liquors N8-5, N8-6 and N8-7 give liquor N8-B (250%, pH 8)

2.2.4. Pickling and Tanning

Below, the data in % by weight are based on the pelt weight, grain split2.8 mm (corresponding to 75% salted weight), unless stated otherwise.Experi- % by Time ment wt. Product pH [min] N8 40 Aqueous, purifiedliquor (N8-A) 10 0.5 PE 11 1.0 Lipoderm fatliquor A1 (diluted 1:3) 200.4 Formic acid (100% strength) (diluted 30 1:5) 0.8 Sulfuric acid (98%strength) 2.9 90 1.8 TA 1 3.4 90 3.0 Basyntan ® SW liquid (diluted 1:2)4.2 900 2.0 Tamol ® NA 1.0 Sodium formate 4.0 90 0.2 Sodium bicarbonate0.2 Cortymol ® FUN (diluted 1:3) 30 Discharge liquor (N8-8 Tanningliquor, 40% by weight)

The remainder of the liquor N8-A (182%, based on the salted weight, pH4.5) and 118% of the liquor N8-B (based on the salted weight, pH 8) werecombined to give the liquor N8-C (300%, based on the salted weight, pH6.5). N8-8 (30%, based on the salted weight, pH 4.5) and 71% of theliquor N8-B (based on the salted weight, pH 8) were disposed of.

2.3. Assessment of the Conventional Procedure C2 and of the NovelProcedure N8 According to Liming and the Corresponding Residual Liquors

The pelts obtained by the novel procedure are equivalent with regard toswelling to those obtained by the conventional procedure but aredistinguished by a smoother and flatter grain. The epidermis and thehairs with hair roots have been completely destroyed.

The residual liquors of the novel procedure can be acidified to pH 4.5with organic or, preferably, inorganic acids, e.g. sulfuric acid,without evolution of hydrogen sulfide, and the precipitated proteins canbe separated off without problems by filtration. The residual liquorsprepared in this manner are as a rule clear.

2.4. Further Processing of Comparative Example C2 and of Novel ExampleN8 in Retanning

The procedure was as shown in the table below. % by Temp. pH Time wt.Product (° C.) N8 C2 [min] 150 Water 30 10 4.0 Basyntan ®SW 30 1.5Tamol ®NA 5.4 5.0 20 0.3 Sodium bicarbonate 1.5 Lipoderm ®fatliquor A160 5.4 5.0 30 1.0 Lipoderm ®fatliquor LA Discharge liquor (C2-11Neutralization liquor; N8-9 Neutralization liquor) 150 Water 30 10Discharge liquor (C2-12 Neutralization wash liquor; N8-10 Neutralizationwash liquor) 70 Water 30 15 3.0 Relugan ®RV 10.0 Basyntan ®SW 5.0 4.8 308.0 Tara-Granofin ®TA 4.0 Basyntan ®DLX-N 2.0 Tamol ®NA 5.4 5.1 10 0.5Sodium bicarbonate 2.0 Luganil ®olive brown N complete 120 penetra- tionof dye 0.5 Formic acid (100%) (diluted 15 1:10) Discharge liquor (C2-13Retanning liquor; N8-11 Retanning liquor) 200 Water 60 15 3.0 Lipoderm ®fatliquor FP (diluted 1:3) 6.0 Lipoderm ® fatliquor A1 60 60 2.0Lipoderm ® fatliquor LA 2.0 Lipoderm ® Oil SK (mixed and diluted 1:7)0.1 Formic acid (100%) (diluted 15 1:10) 0.1 Formic acid (100%) (diluted20 1:10) 0.05 Formic acid (100%) (diluted 3.1 3.1 15 1:10) Dischargeliquor (C2-14 Fatliquoring liquor; N8-12 Fatliquoring liquor) 200 Water50 20 Discharge liquor (C2-15 Fatliquoring wash liquor; N8-13Fatliquoring wash liquor) 200 Water 25 15 0.3 Cortymol ®FUN

The leathers thus obtained were sammed and shaved by conventionalmethods. The shaved thickness of the leathers was 2.0-2.2 mm (shavedweight corresponds to 25% salted weight).

The leathers obtained were worked up in a conventional manner and theirphysical properties and performance characteristics were then tested.

2.5. Assessment of the Crust Leathers Obtained by Conventional ProcedureC2 and Novel Procedure N8

The crust leather produced according to the invention does not differ inits haptic and optical properties from the conventional crust leather.Leather having a very good dyeing and a good tight-grained character incombination with very good body and excellent softness with eleganthandle is obtained. Quality of the Stitch tear hair removal, Grainresistance epidermis tightness* according to DIN removal and hide Wetwhite 53331 Procedure pigment removal* leather [N] C2 2 2 140 N8 2 2 176*Evaluation based on rating2.6. Analysis of the Liquors

All liquor data are based on salted weight: Sam- Sulfide COD ple ProcesspH [ppm]* [mg O₂/l] Liquor C2-1 Standard presoaking 1.3 8200 200 liquorC2-2 Standard main soaking 9.5 2.0 11300 100 liquor C2-3 Standard limingliquor 12.3 500 28200 100 (210) C2-4 Standard liming wash 12.3 150 5500150 liquor C2-5 Deliming wash liquor 12.0 31 2500 113 C2-6 Deliming washliquor 11.9 53 1800 113 C2-7 Deliming liquor 8.6 39 900 75 C2-8 Batingliquor 8.0 — 16500 38 C2-9 Bating wash liquor 8.0 — 2400 113 C2-10Tanning liquor 4.0 — 14700 30 Total up to tanning 8100 1030 C2-11Neutralization liquor 5.0 — 18000 38 C2-12 Neutralization wash 5.1 —7150 38 liquor C2-13 Retanning liquor 3.1 — 41500 18 C2-14 Fatliquoringliquor 3.1 — 17000 50 C2-15 Fatliquoring wash liquor 3.1 — 5500 50 Totalup to crust 9100 1223

Sam- Sulfide COD ple Process pH [ppm]* [mg O₂/l] Liquor N8-1 Presoakingliquor 8.3 2.5 14400 200 N8-2 Main soaking liquor 9.4 2.5 17500 100 N8-3Liming liquor 12.4 50 (4) 25800 100 N8-4 Liming wash liquor 12.4 12 5500150 N8-5 Deliming liquor 8.5 6 7000 38 N8-6 Bating liquor 8.0 — 16500 38N8-7 Bating wash liquor 8.0 — 2400 113 N8-8 Tanning liquor 4.0 — 2090030 Total up to tanning 14200 400 N8-9 Neutralization liquor 5.4 — 1500038 N8-10 Neutralization wash 5.4 — 6300 38 liquor N8-11 Retanning liquor3.1 — 37500 18 N8-12 Fatliquoring liquor 3.1 — 10550 50 N8-13Fatliquoring wash liquor 3.1 — 3950 50 Total up to crust 10600 5932.7. Summary of the Results with Hair-Preserving Liming

Comparison for soaking 1 000 kg salted weight: Water Water consumptionconsumption up to up to COD_(total) Experi- tanning tanning COD [kg CODment [m³] [rel. %] [mg O₂/l] O₂/kg] [rel. %] C2 10.30 100 8100 83.4 100N8 4.01 39 14200 56.8 68

Water Water consumption consumption COD_(total) Experi- up to crust upto crust COD [kg COD ment [m³] [rel. %] [mg O₂/l] O₂/kg] [rel. %] C212.23 100 9100 111.3 100 N8 5.93 48 10600 62.9 57

Protein precipitate from N8:

-   N8: Yield: 100 kg, dry substance: 30%, COD [kg O₂/kg]: 18.9 Ash    content: 1.0%

Worked-up and reused liquors from N8: COD DS Ash [mg Liquor LiquorProcess pH [%] [%] O₂/l] [%] N8-A N8-3 + N8-4 (before 12.5 7.8 0.8 38600250 precipitation) N8-A N8-3 + N8-4 (after 4.5 5.7 2.6 6200 250precipitation) N8-B N8-5 + N8-6 + N8-7 8 1.7 0.5 6100 189 N8-C N8-A(182%) + N8-B 6.5 4.1 1.2 6200 300 (118%) N8-D N8-1 + N8-2 + N8-B 6.5 —— 14200 401 (71%) + N8-8

3. Overall Comparison for Soaking for 1 000 kg Salted Weight Water Waterconsumption consumption COD Experi- up to up to tanning [mg COD_(total)COD ment tanning [m³] [rel. %] O₂/l] [kg O₂] [rel. %] C1 10.80 100 12600136.2 100 C2 10.30 95 8100 83.4 61 N1 7.68 71 18000 138.2 101 N2 7.68 7117900 137.4 101 N3 7.68 71 17900 137.3 101 N4 7.68 71 18000 138.3 102 N57.68 71 18300 140.2 103 N6 4.01 37 18300 73.2 54 N7 4.01 37 14500 58.043 N8 4.01 37 14200 56.8 42

Water Water consumption consumption COD Experi- up to up to crust [mgCOD_(total) COD ment crust [m³] [rel. %] O₂/l] [kg O₂] [rel. %] C1 12.73100 12900 164.1 100 C2 12.23 96 9100 111.3 68 N1 9.60 75 16700 160.0 97N2 9.60 75 16500 158.8 97 N3 9.60 75 16600 159.2 97 N4 9.60 75 16700160.3 98 N5 9.60 75 16900 162.2 99 N6 5.93 47 14200 84.2 51 N7 5.93 4710800 64.0 39 N8 5.93 47 10600 62.9 38

The overall comparison of the preceding tables shows in an impressivemanner that the water consumption in the novel production of leather canbe reduced to about 70 to 75% and, with liquor recycling, a preferrednovel procedure, even to about 40 to 50% of the water consumption of theconventional procedure.

FIG. 1 and FIG. 2 once again give an overview of the water/wastewaterstreams (liquor streams) in the beamhouse for the conventional procedureC1 (also applies in context to procedure C2) and the preferred novelprocedures NX (X=6, 7 or 8) with liquor recycling. As stated at theappropriate points, the percentages of water/wastewater streams (liquorstreams) are based on the salted weight of the hides and are shown underpoint 1.7. Analysis of the liquors (for C1, N6 and N7) and point 2.6.Analysis of the liquors (for N8) in the respective tables.

It is furthermore advantageous that the protein (hydrolysis product)present in the liquor after the liming can for the most art be removedby the novel procedure by acidic precipitation and, owing to its lowcontent of inorganic salts (cf. the abovementioned ash contents), can beused for a high-quality application, e.g. as a feed additive.

The decrease in the concentration of organic pollutants produced in thewastewaters of the beamhouse—depending on the procedure, the absoluteCOD value can be reduced to about 40 to 50% of the value for theconventional procedure—furthermore leads to a substantial cost reductionin their disposal (note: owing to the lower water consumptions in thenovel procedure, the concentration data for the COD are for the mostpart higher than in (hair-destroying) procedure C1. If, however, theabsolute COD values (COD total) or the relative amounts based on theabsolute COD value of C1 are considered, said reductions in organicpollutants in the wastewater result in particular for experiments N6 toN8 (liquor recycling after prior protein precipitation).

1. A process for the production of leather, comprising at least two ofthe following process steps A) to D): A) use of one or morepolyelectrolytes in the production of semifinished products orintermediate products, comprising at least one of the steps (a) to (d)(a) addition of one or more polyelectrolytes and from 0 to 1.5% byweight, based on the salted weight, of lime, immediately before orduring liming, (b) addition of one or more polyelectrolytes before orduring deliming, (c) addition of one or more polyelectrolytes before orduring bating, (d) addition of one or more polyelectrolytes and,altogether, from 0 to 3% by weight, based on the pelt weight, of alkalimetal or alkaline earth metal salt, immediately before or duringpickling; B) treatment of the hides during liming in aqueous liquor withone or more compounds of the formula B.1

 or the corresponding alkali metal, alkaline earth metal, ammonium orphosphonium salts thereof, wherein: R¹⁰ is hydrogen or C₁-C₁₂-alkylwhich is unsubstituted or substituted by one or more mercapto orhydroxyl groups, X₁ to X⁴, independently of one another, are hydrogen,C₁-C₄-alkyl, hydroxyl, mercapto or NHR¹¹ and R¹¹ is hydrogen,C₁-C₁₂-alkyl, formyl or C₁-C₄-alkylcarbonyl, wherein at least twomercapto groups are comprised in the compound or the compounds B.1; C)use of degreasing agents of the formula C.1

 for degreasing pelts, hides or other intermediate products andsemifinished products in leather production, wherein: R¹⁶ to R¹⁹,independently of one another, are hydrogen or branched or straight-chainC₁-C₁₀-alkyl, R₂₀ is hydrogen or C₁-C₂₅-alkyl, R₂₁ is hydrogen orC₁-C₄-alkyl and n is an integer from 1 to 100, R¹⁶ corresponding toC₁-C₁₀-alkyl when R¹⁸ to R²⁰ are each hydrogen and at least one of theradicals R¹⁸ to R²⁰ corresponding to C₁-C₂₅-alkyl when R¹⁶ is hydrogen;D) tanning with the use of a tanning agent which can be prepared byreacting at least one aldehyde of the formula D.1,

 with at least one further identical or different aldehyde of theformula D.1, wherein: Z is a single chemical bond, unsubstituted orsubstituted C₁-C₁₂-alkylene, unsubstituted or substitutedC₅-C₁₂-cycloalkylene or unsubstituted or substituted C₆-C₁₄-arylene, thereaction being carried out in the presence of an acidic catalyst andoptionally in the presence of at least one further carbonyl compound ofthe formula D.2

 wherein: R²² to R²⁵, independently of one another, are hydrogen,unsubstituted or substituted C₁-C₁₂-alkyl, unsubstituted or substitutedC₃-C₁₂-cycloalkyl, unsubstituted or substituted C₇-C₁₃-aralkyl orunsubstituted or substituted C₆-C₁₄-aryl, wherein at least one furtheraldehyde of the formula D.1 in which Z comprises a-hydrogen atoms, or atleast one further carbonyl compound of the formula D.2, is present whenZ corresponds to a single chemical bond or to a radical withouta-hydrogen atoms.
 2. A process as claimed in claim 1, comprising theprocess steps A) and B).
 3. A process as claimed in claim 1, comprisingthe process steps A), B) and C).
 4. A process as claimed in claim 1,comprising the process steps A) to D).
 5. A process as claimed in claim2, wherein the step (a) is comprised in process step A).
 6. A process asclaimed in claim 1, wherein no lime (0% by weight of lime) is used instep (a) of process step A).
 7. A process as claimed in claim 1, whereinone or more hydroxylamine compounds of the formula A.15.a or A.15.b

 or one or more unprotonated or protonated hydrazine compounds of theformula A.16

 are additionally introduced in step (a) of process step A), wherein R⁶to R⁹, independently of one another, are hydrogen, C₁-C₂₀-alkyl orC₆-C₁₄-aryl and An⁻ is halide, sulfate, hydrogen sulfate, phosphate,hydrogen phosphate or dihydrogen phosphate or a mixture of said anions.8. A process as claimed in claim 7, wherein hydroxylamine is added instep (a) of process step A).
 9. A process as claimed in claim 5, whereinalkali metal hydroxide and/or alkali metal carbonate are additionallyused in step (a) of process step A).
 10. A process as claimed in claim5, wherein the process water obtained after combination of process stepA) (a) and process step B) and substantially freed from the organiccomponents, is used at least partly in at least one further step ofprocess steps A)(b) to A)(d), C) and D) for the production of leatherand/or for the presoak and main soak of the rawhides.
 11. A process asclaimed in claim 10, wherein the process water obtained aftercombination of process step A) (a) and process step B) and substantiallyfreed from the organic components, is used at least partly in step (b)of process step A) and/or in process step D) and/or for the presoak andmain soak of the rawhides.
 12. A process water substantially freed fromorganic components, obtained after combination of process step A) (a)and process step B) by a process for the production of leather asclaimed in claim
 5. 13. A leather which has been produced by a processas claimed in claim 1.